flit 


D. 


GDIFT  OF 
DEWITT  BISHOP 


COLLEGE  OF  AGRICULTURE 
DAVIS,  CALIFORNIA 


MB' LIBRARY 


~ 


OUR  INSECT  FRIENDS  AND  ENEMIES 


I 

y  «*. 


',<   V    . 


10 


11 


1.  The  oriental  roach  or  "  black  beetle  "  :  male. 

2.  The  oriental  roach  or  "  black  beetle  "  :  female. 

3.  The  German  roach  or  "  croton  bug  "  :  male. 

4.  The  German  roach  or  "  croton  bug  "  :  female,  with  egg  case. 

5.  Egg  of  bed-bug. 

6.  Bed-bug. 

7.  Caterpillar  of  a  "  clothes-moth  "  in  its  case. 

8.  One  of  the  common  "  clothes-moths." 

9.  The  "  buffalo  moth  "  or  "  bug." 

10.  The  parent  beetle  of  the  "  buffalo  moth." 
it.  Egg  of  a  flea. 

12.  A  flea  larva. 

13.  The  common  dog  flea. 

14.  The  little  red  house-ant. 

All  of  the  figures  are  very  much  enlarged  and  most  of  them  were  re-drawn 
from  the  Bulletins  and  Reports  of  the  Division  of  Entomology,  U.  S.  Department 
of  Agriculture. 


OUR  INSECT  FRIENDS 
AND  ENEMIES 

THE  RELATION  OF  INSECTS  TO  MAN,  TO  OTHER 
ANIMALS,   TO   ONE   ANOTHER,  AND   TO   PLANTS 

WITH  A  CHAPTER  ON 

THE  WAR  AGAINST  INSECTS 


BY 
JOHN  B.  SMITH,  Sc.D. 

PROFESSOR  OF   ENTOMOLOGY  IN   RUTGERS   COLLEGE;    ENTOMOLOGIST  TO   THR 
NEW   JERSEY   AGRICULTURAL   EXPERIMENT   STATIONS;    NEW  JERSEY 

STATE  ENTOMOLOGIST;  MEMBER  AND  FELLOW  OF  A.  A.  A.  s.; 

N.    Y.    ACADEMY   OF   SCIENCES;     ENTOMOLOGICAL 
SOCIETY  OF   AMERICA  ;     ETC.,  ETC. 


PHILADELPHIA  &•  LONDON 

J.  B.  LIPPINCOTT   COMPANY 
1909 


COPYRIGHT,  1909 
BY  J.  B.  LIPPINCOTT  COMPANY 


Published  April,  1909 


Electrotyped  and  printed  by  J.  B.  Lippincott  Company 
The  Washington  Square  Press,  Philadelphia,  U.  S.  A. 


FOREWORD 

NOTHING  in  this  world  of  ours  exists  to,  for  or  by 
itself  alone.  Every  living  creature  depends  upon  some 
other  form  of  life,  or  upon  inorganic  matter  and  is,  in 
turn,  the  dependence  of  others  that  find  it  useful  or 
essential  for  continued  existence.  And  as  inorganic 
matter  is,  after  all,  the  base  of  organic  matter  as  we 
know  it,  plus  the  addition  that  makes  it  organic  and 
whose  nature  we  do  not  yet  know,  so  in  due  course  all 
organised  forms  again  return  to  their  lifeless  constituents. 

Every  living  thing,  then,  has  relations  to  many 
other  living  things  and  some  of  these  relations,  so  far 
as  insects  are  concerned,  it  is  my  object  to  present. 
I  need  hardly  disclaim  any  attempt  at  completeness; 
but  so  far  as  the  presentation  goes  it  claims  accuracy. 
A  large  proportion  of  the  facts  have  been  personally 
observed  or  verified,  others  are  common  knowledge 
and  all  are  based  upon  the  observations  or  records  of 
scientific  investigators. 

Some  of  these  relations  of  insects  to  the  welfare  of 
man  have  been  but  recently  worked  out  and  are  imper- 
fectly known;  yet  enough  has  come  to  the  general 
information  to  arouse  a  decided  interest  in  these  long 
despised  creatures.  Their  presence  or  absence  from  our 
midst  may  make  all  the  difference  between  sickness 
and  health,  irritation  and  comfort,  poverty  or  wealth, 
or,  on  the  other  hand,  wealth  and  poverty.  They  make 
some  regions  uninhabitable  that  would  otherwise  be 
attractive  as  sites  for  homes  and,  altogether,  their 
influence  upon  humanity,  directly  and  indirectly,  is 
vastly  greater  than  is  generally  realized. 

5 


72685 


ACKNOWLEDGMENTS 

Of  the  figures  illustrating  this  work,  the  following 
were  drawn  for  me  by  Mr.  John  A.  Grossbeck,  my  as- 
sistant, from  originals  or  modified  from  published 
sources:  i,  4,  5,  6,  7,  8,  10,  n,  13,  18,  19,  20,  22,  24, 
34,  41,  61,  64,  65,  66,  67,  68,  70,  71,  80,  81,  87,  89,  92, 
93>  94,  95'  96,  104,  107. 

From  the  publications  of  the  Entomological  Division 
of  the  U.  S.  Department  of  Agriculture  the  following 
were  obtained,  either  as  electrotypes  or  as  copies  from 
the  prints:  9,  49,  63,  77,  91,  98,  100,  101,  103,  no,  112, 

113- 

From  the  New  Jersey  Agricultural  College  Experi- 
ment Station  I  obtained  blocks  for  figures  48  and  99. 

The  other  blocks  are  by  courtesy  of  the  J.  B.  Lip- 
pincott  Company  from  my  "Economic  Entomology," 
where  their  original  source  is  stated;  but  a  number  of 
them  have  been  somewhat  reduced  in  size. 


CONTENTS 


I.     INSECTS  IN  THEIR  RELATION  TO  THE  ANIMAL  KING- 
DOM           9 

II.     INSECTS  IN  THEIR  RELATION  TO  PLANTS  AS  BENE- 
FACTORS      21 

III.  INSECTS   IN  THEIR   RELATION  TO   PLANTS   AS   DE- 

STROYERS       40 

IV.  INSECTS  IN  THEIR  RELATION  TO  EACH  OTHER 84 

V.     INSECTS  IN  THEIR  RELATION  TO  THE  ANIMALS  THAT 

FEED  ON  THEM 130 

VI.     INSECTS  IN  THEIR  RELATION  TO  WEATHER  AND  DIS- 
EASES THAT  AFFECT  THEM 138 

VII.     INSECTS  IN  THEIR  RELATION  TO  OTHER  ANIMALS.  ...    1 53 

VIII.     INSECTS  IN  THEIR  RELATION  TO  MAN:  AS  BENEFAC- 
TORS .... , 185 

IX.     INSECTS  IN  THEIR  RELATION  TO  MAN:  AS  CARRIERS 

OF  DISEASES *99 

X.     INSECTS  IN  THEIR  RELATION  TO  THE  HOUSEHOLD..  .   217 

XI.     INSECTS  IN  THEIR   RELATION  TO  THE  FARMER  AND 

FRUIT-GROWER 249 

XII.     THE  WAR  ON  INSECTS 271 

INDEX 309 


OUR  INSECT  FRIENDS 
AND  ENEMIES 


CHAPTER  I 

THEIR  RELATION  TO  THE  ANIMAL  KINGDOM 

IF  we  examine  any  insect,  large  or  small,  in  any 
save  the  egg  stage,  we  note  at  once  that  it  has  its  skeleton 
on  the  outside  of  the  body.  Not  much  of  a  skeleton  in 
some  cases,  e.g.,  a  caterpillar,  a  slug  or  a  maggot;  a 
very  resistant  and  rigid  shell  or  body  wall  in  others,  as 
in  some  beetles  which  may  be  run  over  by  a  heavy 
wagon  wheel  without  being  any  the  worse,  or  may  pass 
unchanged  through  the  digestive  system  of  a  toad. 
In  any  event  it  serves  for  the  attachment  of  the  muscles 
on  the  inside,  and  they  are  thus  protected,  instead  of 
sheltering  and  protecting  an  inside  bony  framework  as 
in  man  and  other  vertebrate  animals. 

It  will  be  further  seen,  especially  in  the  simpler 
forms,  that  the  body  is  made  up  of  successive  rings  or 
joints,  more  or  less  similar  in  the  primitive  types,  often 
very  unlike  in  the  higher  orders,  and  that  the  legs  also 
are  made  up  of  a  number  of  parts  or  segments.  These 
characters  place  the  insects  with  that  great  section  of 
the  animal  kingdom  known  as  Articulata,  which  includes 
everything  from  an  earthworm  to  a  lobster,  and  more 
narrowly  restricts  them  to  the  Arthropods,  which  have 
jointed  legs,  and  thus  exclude  the  worms;  but  still 
leaves  the  lobster  as  a  relative. 

9 


io  INSECTS 

Matters  now  become  a  little  more  difficult;  but  if 
we  continue  our  examinations  by  comparing  a  lobster, 
a  spider  and  a  beetle,  we  find  that  the  latter  has  a 
distinct  head,  separate  from  the  rest  of  the  body,  while 
in  the  others  the  head  and  middle  section  of  the  body 
form  a  single  mass  known  as  a  "  cephalothorax. "  Our 
beetle  also  will  be  found  to  be  breathing  from  the  sides 
of  the  body  through  a  series  of  ringed  tubes  known  as 
trachea  and  this  makes  it  a  Tracheate — an  honor  that  it 
shares  with  centipedes  or  myriapods.  Finally,  if  we 
persist  in  our  policy  of  exclusion,  we  leave  as  true 
insects  only  those  forms  that  have  no  more  than  three 
pairs  of  jointed  legs,  attached  to  the  thorax  or  middle 
region  of  the  body,  the  body  itself  made  up  of  no  more 
than  thirteen  obvious  rings  or  segments,  grouped  into 
three  regions,  the  head,  thorax,  and  abdomen,  contain- 
ing respectively  one,  three  and  nine  segments. 

We  are  now  ready  to  define  an  insect  as  an  articulate, 
arthropod,  tracheate  hexapod;  but  it  will  be  equally 
correct  and  much  easier  to  say  that  it  is  a  ringed  ani- 
mal, with  six  jointed  legs,  breathing  by  means  of  air 
tubes  or  tracheae;  this  definition  applying  more  particu- 
larly to  the  adult  stage,  and  only  to  the  adult  stage  of 
many  of  those  having  a  complete  metamorphosis. 
.  This  method  of  breathing,  by  the  bye,  carries  with 
it  a  modification  of  the  circulating  system.  The  air 
being  carried  in  tubes  to  all  parts  of  the  body,  there  is 
no  need  for  lungs  nor  for  any  system  of  veins  or  arteries. 
The  blood  simply  flows  about  in  the  interstices  of  the 
body  cavity,  kept  in  motion  by  a  tube-like  heart,  divided 
into  chambers,  which  lies  just  under  the  back  or  dorsal 
surface,  and  oxygen  is  taken  up  from  the  tracheae  any- 
where in  its  course,  while  the  products  of  digestion  are 
taken  up  from  the  specialized  cells  about  the  digestive 
system.  And,  after  all,  the  process  of  maintaining  life 


RELATION  TO  ANIMAL  KINGDOM 


ii 


..- 


12  INSECTS 

and  activity  is  much  the  same  among  insects  as  it  is 
in  the  higher  animals,  although  the  method  is  some- 
what different.  The  blood  is  equally  the  agent  for 
transporting  nutritious  material  to  whatever  point  it 
may  be  needed,  and  the  oxygen  to  burn  out  waste 
products  is  as  essential. 

Under  the  microscope,  insect  muscle  is  not  so  very 
different  from  that  of  man:  it  has  similar  transverse 
striations,  and  contracts  and  extends  in  a  similar 
manner,  but,  nevertheless,  there  is  no  chance  of  con- 
fusing insect  with  vertebrate  muscle.  This  muscular 
system  is  under  the  control  of  a  nervous  system  which 
is  very  highly  developed  in  detail,  but  consists  essen- 
tially of  a  double  cord  extending  from  one  end  of  the 
body  to  the  other,  lying  just  above  the  under  or  ventral 
surface  and  furnished  with  a  series  of  enlargements  or 
ganglia,  of  which  that  lying  in  the  head  and  termed  the 
brain  is  the  largest,  although  it  exercises  no  such  dominant 
influence  as  does  that  organ  in  the  higher  vertebrates. 

There  is  quite  a  difference,  of  course,  among  insects, 
in  the  amount  of  specialization  in  this  nervous  system. 
In  some  and  especially  in  larval  forms  all  the  ganglia 
are  similar  in  size  and  appearance,  and  there  is  one  for 
every  segment;  in  others  the  tendency  to  centraliza- 
tion is  marked,  all  the  thoracic  ganglia  being  united  into 
one,  while  in  the  abdomen  two  or  three  of  the  posterior 
ganglia  join  in  the  control  of  the  reproductive  system 
and  the  various  accessory  parts  connected  with  it.  The 
thoracic  centre  controls  the  organs  of  locomotion  and  a 
paralysis  that  is  practical  death  results  immediately 
when  this  ganglion  is  cut,  whereas  we  can  cut  off  the 
head  and  abdomen,  of  a  house-fly  for  instance,  without 
interfering  with  its  power  to  use  legs  or  wings.  This 
fact  was  known  to  the  digger  wasps  long  before  the 
entomologist  knew  it,  for  when  such  a  digger  wishes  to 


RELATION  TO  ANIMAL  KINGDOM  13 

quiet  its  prey  ^before  carting  it  home,  the  sting  is  aimed 
at  this  very  ganglion  with  instantaneous  results. 

As  to  senses,  the  insects  have  all  those  of  other 
animals  and  perhaps  more,  too;  but  developed  in  an 
altogether  different  way  and  to  a  very  diverse  extent. 
Insects  see  and  have  the  most  complicated  kinds  of 
eyes  known,  as  well  as  almost  the  simplest  in  existence. 
Some  species  are  sensitive  to  rays  of  light  which  man 
cannot  see  at  all  and  some  species  certainly  seem  to 
see  better  at  night  than  during  the  day.  But,  on  the 
other  hand,  it  is  doubtful  whether  they  see  at  all  dis- 
tinctly or  can  recognize  form  and  color  when  not  directly 
connected  with  their  life-needs.  So  they  can  hear; 
some  of  them  very  acutely,  and  ears  are  by  no  means 
confined  to  the  head:  they  may  be  on  the  feet,  the  body, 
the  abdomen  or  on  the  antennae,  and  it  is  believed  that 
they  hear  sounds  so  high  in  pitch  that  they  are  beyond 
the  reach  of  our  senses.  Nevertheless  it  is  almost  equally 
certain  that  they  are  probably  incapable  of  discriminat- 
ing between  sounds,  and  of  really  recognizing  any  but 
those  connected  with  the  sexual  calls  of  their  mates  or 
perhaps  the  noises  made  by  their  prey  and  possibly 
their  enemies.  Insects  certainly  have  the  sense  of  taste 
and  some  of  the  most  elaborate  taste  organs  are  found 
in  species  feeding  on  the  vilest  excrementitious  material. 
Perhaps  the  less  we  say  on  this  point  the  better, 
unless  it  is  to  suggest  that  there  are  gustatory  possi- 
bilities that  man  is  utterly  incapable  of  appreciating. 
Insects  smell,  and  this  sense  is  most  acutely  developed. 
The  male  seeks  and  finds  the  female  almost  entirely 
by  this  sense  even  when  she  is  carefully  and  intentionally 
hidden  from  sight,  and  both  sexes  find  their  food  by 
this  sense  more  often  than  by  sight:  and  that  is  particu- 
larly true  of  those  forms  that  feed  on  fermenting  or 
decaying  matter.  Insects  feel,  no  doubt,  and  the  tac- 


i4  INSECTS 

tile  sense  is  popularly  and  probably  with  _,  ,'tice  located 
chiefly  in  the  antennae;  but  the  mouth  feelers  or  palpi 
are  also  organs  of  touch  and  tactile  hairs  may  occur  on 
any  part  of  the  body  or  its  appendages.  No  one  insect 
species  has  all  these  senses  equally  well  developed,  and 
few  have  more  than  one  or  two  really  so  specialized  as 
to  be  conspicuous.  There  are  more,  indeed,  which  have 
none  of  them  more  than  rudimentarily  present  and 
probably  a  fairly  well-developed  general  sense  of  per- 
ception is  enough  for  the  majority.  Such  a  sense  enables 
the  insect  to  recognize  the  vibrations  that  mean  food, 
a  mate  and  a  place  to  oviposit  and  that  is  all  that  is 
really  necessary  to  enable  it  to  fill  its  place  in  life.  As 
to  that  tactile  sense  that  implies  a  recognition  of  what 
we  know  as  pain,  I  believe  it  to  be  very  feebly  developed. 
I  do  not  indeed  assert  that  insects  are  insensible  to  pain ; 
but  all  observations  indicate  that  they  appreciate  it 
very  little  and  very  temporarily:  real  suffering  I  do 
not  believe  them  capable  of  at  all. 

An  interesting  question  that  is  often  raised  in  this 
connection  is  whether  insects  reason  or  whether  all 
their  actions  are  instinctive.  I  do  not  believe  that 
any  one  can  study  insects  at  all  closely  without  crediting 
them  with  a  certain  amount  of  reasoning  power.  Some 
species  do  such  incredibly  stupid  things  occasionally 
that  it  would  be  a  libel  on  instinct  to  charge  it  with  such 
actions,  and  often  specimens  of  the  same  species  will 
do  things  so  differently  that  individuality  and  ratio- 
cination must  be  accepted  as  accounting  for  the  differ- 
ence. To  be  sure  it  is  not  a  very  high  grade  of  intelli- 
gence that  is  manifested,  using  our  own  attainments  as 
a  standard;  but  it  is  such  a  grade  as  brings  out  the 
difference  between  individuals  and  species  and  enables 
one  to  do  well  what  the  other  fails  in,  habitually.  It  is 
in  the  Hymenoptera  and  especially  among  the  social  forms 


RELATION  TO  ANIMAL  KINGDOM  15 

that  this  intelligence  is  best  manifested ;  but  I  have  noted 
it  in  the  majority  of  the  species  that  I  have  observed  at 
all  carefully  in  the  open,  under  natural  conditions  rather 
than  in  the  laboratory  in  artificial  surroundings. 

Insects  are  as  a  rule  prolific  breeders,  although 
there  is  a  great  difference  between  them  in  this  respect: 
some  multiply  only  ten-fold  in  the  course  of  the  season, 
while  in  others  the  capacity  is  1,000,000,000  descendants 
in  the  same  period.  No  one  has  actually  counted  that 
number,  of  course,  but  we  have  counted  the  number 
born  to  a  single  pair  and  determined  the  number  of 
broods  to  the  season;  so  it  is  a  mathematical  certainty, 
even  if,  as  a  matter  of  fact,  probably  no  one  pair  ever 
matured  all  its  offspring  for  as  many  successive  genera- 
tions as  are  required  to  produce  such  a  result. 

In  their  development  there  is  considerable  variety, 
but  as  a  rule  they  pass  through  four  more  or  less  distinct 
stages:  this  being  called  transformation  or  metamor- 
phosis, while  the  various  stages  are  also  called  instars. 

The  first,  or  egg-stage,  is  usually  quiescent  and  gen- 
erally passed  outside  the  insect  body ;  but  in  some  cases 
it  hatches  within  the  ovary  of  the  mother  and  young  are 
born  alive,  as  in  many  plant  lice  and  scale  insects.  Spe- 
cies may  therefore  be  oviparous  (egg-bearing),  or  vivip- 
arous (live-bearing),  the  latter  also  termed  larviparous. 

The  second,  or  larval  stage,  is  that  which  hatches 
from  the  egg,  and  it  may  or  may  not  be  like  the  parent. 
In  the  grasshopper,  for  instance,  we  can  recognize  it 
as  such,  no  matter  how  recently  hatched;  but  in  the 
minute  caterpillar,  just  out  of  the  shell,  no  resemblance 
to  the  butterfly  can  be  traced.  The  larval  stage  is  the 
period  of  growth:  the  insect  feeds  to  the  limit  of  the 
elasticity  of  its  integument  or  outer  skeleton,  then 
sheds  this  skin  or  "moults,"  and  repeats  this  process 
until  it  has  reached  its  limit  of  size. 


i6 


INSECTS 


It  may  be  well  to  say  just  a  few  words  as  to  this 
outer  skin  which  forms  so  important  a  feature  in  the 
insect  structure.  It  is  soft  yet  resistant,  and  may 
become  so  resistant  that  it  is  almost  impenetrable  to 
corrosives  or  oils  and  with  difficulty  to  be  punctured 
with  needle  or  knife.  It  all  depends  upon  the  amount 
of  chitin  deposited  in  the  tissue  and  chitin  is  a  secre- 
tion from  the  lower  layers  of  the  cuticle,  resembling 
horn  in  texture  and  somewhat  in  qualities.  No  matter 


FIG.  2. — Moulting  of  a  grasshopper:  a,  nymph  ready  to  change ;  b,  the  skin 
split  along  the  back  and  the  adult  emerging;  c,  continues  the  process,  and  at  d, 
the  insect  is  drying  out. 


how  soft  the  body  wall  it  contains  some  chitin  and  as 
this  is  not  elastic,  there  is  a  limit  beyond  which  it  cannot 
be  stretched.  When  this  limit  is  reached  a  new  skin 
forms  beneath  the  old  one  which,  thereupon  becoming 
lifeless,  splits  and  permits  the  larger  next  stage  to  escape. 
This  sort  of  change  is  found  also  in  the  crustaceans, 
and  in  some  of  the  reptiles. 

The  third,  or  pupal  stage,  may  be  a  period  of  rest 
or  of  continued  activity,  depending  upon  whether  the 
species  has  a  "complete"  or  an  "incomplete"  meta- 
morphosis. Returning  again  to  our  young  grasshopper, 


RELATION  TO  ANIMAL  KINGDOM  17 

usually  called  a  "nymph"  rather  than  a  larva,  when 
this  has  become  ripe,  it  develops  wing  pads  or  rudimen- 
tary wings ;  but  continues  its  feeding  as  in  the  preceding 
stages  until  the  period  when  it  moults  for  the  last  time 
and  changes  to  the  adult  or  fourth  stage.  It  thus 
develops  continuously,  without  conspicuous  change  of 
form,  and  the  metamorphosis  is  incomplete.  Our 
caterpillar,  however,  after  moulting  as  often  as  needed 
to  obtain  full  size,  changes  into  a 
nondescript  creature  bearing  no  close 
resemblance  to  its  former  nor  to  its 
future  stage  and  remains  in  this 
"pupal"  or  "chrysalis"  form  while  FlG.3._Sectionthrough 
the  caterpillar  structures  are  disin-  insect  crust  showing  iay- 

-...-.  ers  of  chitin  at  c,  the  cel- 

tegrated  and  re-formed  into  butter-     luiar  layer  at  h,  and  the 
fly  parts.    This  is  a  complete  trans- 
formation, in  which  almost  no  part 
of  the   larval  structure  remains  unchanged,  and  even 
the  method  of  feeding  may  become  completely  reversed: 
indeed,   in    some   cases   the   adults   never   feed   at   all, 
depending  entirely  upon«the  supply  stored  by  the  larva 
to  mature  the  reproductive  cells  or  eggs. 

Among  themselves  insects  differ  as  much  in  appear- 
ance and  habits  as  they  do  from  their  more  remote 
relations.  They  are  found  wherever  life  is  capable  of 
existing  at  all,  and  there  is  no  organic  substance  known 
which,  in  one  stage  or  another,  is  not  food  for  some 
insect.  They  are  moderately  numerous,  some  200,000 
different  kinds  being  already  known  and  described, 
with  the  reasonable  certainty  that  we  have  not  yet 
discovered  much  more  than  one-half  of  those  that  exist. 

There  are  some  that  never  become  winged;  that  are 
soft -bodied  in  all  stages,  live  usually  in  damp  places 
and  are  simply  organized:  these  are  the  Thysanura,  in 
which  the  mouth  structure  is  not  well  developed. 


1 8  INSECTS 

A  very  decided  advance  is  found  in  those  insects 
that  gain  their  food  by  sucking  it  through  a  jointed 
beak  by  means  of  slender,  bristle-like  lancets  in  all 
stages;  and  these  are  the  Hemiptera  or  true  bugs. 

Grasshoppers,  roaches,  crickets  and  the  like  have 
the  hind  wings  folded  in  longitudinal  plaits,  laid  straight 
under  the  covering  primaries,  and  are  hence  called 
Orthoptera.  They  chew  their  food  and  are  often  trouble- 
some to  the  agriculturist. 

Another  large  series  has  the  wings  thin,  transparent, 
usually  of  good  size,  with  numerous  longitudinal  and 
transverse  veins  like  a  net  or  reticule  and  hence  called 
Neuroptera.  This  is  the  most  primitive  of  the  winged 
orders  of  biting  insects,  and  shows  a  great  diversity  of 
forms  and  grades  of  development.  The  dragon  flies 
serve  as  a  well-known  illustration  of  one  type.  The 
very  general  definition  of  the  order  here  given  covers  a 
series  of  remnants  that  are  elsewhere  more  particularly 
specified.  It  was  in  the  Neuropterous  or  net-winged 
type  that  the  great  break-up  among  the  mandibulate 
insects  occurred  and  variation  ran  in  many  directions. 
Some  of  the  lines  flourished  for  a  little  time  only;  they 
proved  ill  adapted  to  their  surroundings  and  survive 
only  by  a  few  families  and  genera  in  which  the  species 
are  usually  well  fixed  and  easily  distinguished.  Others, 
well  suited  to  live,  proved  barren  when  it  came  to  adapt- 
ing themselves  to  new  or  a  variety  of  conditions.  These 
are  fairly  numerous  even  now  in  families,  genera  and 
species;  but  their  limit  of  adaptation  is  reached  and 
they  are  shoots  from  which  no  further  branches  may 
be  expected.  From  the  other  lines  the  modern  domi- 
nant orders  developed  which,  rich  in  forms,  show 
species  capable  of  living  under  the  greatest  conceivable 
variety  of  conditions. 

The  Coleoptera  or   beetles   are  known  by  the   hard 


RELATION  TO  ANIMAL  KINGDOM  19 


FIG.  4.— The  orders  of  insects:  i,  a  bristle  tail  and  2,  a  spring  tail,  are  Thysa- 
nura;  3,  a  dragon  fly  and  4,  a  Psocid,  illustrating  Neuroptera;  5,  a  grasshopper 
illustrating  Orthoptera;  6,  a  shield  bug  represents  Hemiptera;  7,  a  ground 
beetle  shows  Coleoptera;  8,  a  butterfly,  illustrating  Lepidoptera;  9,  a  horse-fly 
represents  the  Diptera,  and  10,  a  bumble-bee,  the  Hymenoptera. 


20  INSECTS 

or  leathery  fore-wings,  beneath  which  the  membranous 
secondaries  are  transversely  folded.  They  gain  their 
food  by  chewing,  in  all  stages,  although  the  early  or 
larval  forms  are  usually  altogether  unlike  the  adults. 

The  Lepidoptera  include  the  butterflies  and  moths, 
known  by  the  scaly  covering  of  the  wings.  The  scales 
appear  as  fine,  dust-like  particles  that  are  easily  rubbed 
off;  but  under  the  microscope  show  great  differences 
in  form  and  color.  In  this  order  the  mouth  parts  of  the 
adult  are  modified  into  a  coiled  tongue  capable  of  sipping 
liquids  only ;  but  in  the  larval  stage  the  caterpillars  are 
voracious  devourers  of  plant  and  other  tissue. 

Bees,  ants,  wasps  and  the  like  belong  to  the  order 
Hymenoptera,  in  which  the  wings  are  transparent,  with 
few  and  often  no  veins;  never  reticulated.  Many  of 
the  species  are  of  extreme  interest  because  of  their 
social  habits  and  organizations,  and  the  honey  bee  is  of 
direct  benefit  to  man  in.  more  ways  than  one. 

Finally  come  the  flies ;  differing  from  all  other  insects 
by  having  only  one  pair  of  wings,  whence  their  ordinal 
name  Diptera.  We  shall  have  more  to  say  concerning 
some  of  their  species  and  development  elsewhere. 

The  insects  as  a  whole  are  at  the  top  of  the  line  of 
development  in  the  Articulata:  they  diverged  early 
from  the  worm-like  ancestors  and  their  remains,  already 
well  developed,  are  found  in  the  earliest  fossil-bearing 
strata.  At  the  present  time  there  are  more  species  of 
insects  than  there  are  of  all  other  species  of  animals 
taken  together,  and  in  number  of  individuals  they  are 
unapproachable.  The  class  as  a  whole  is  yet  a  growing 
one  and  both  genera  and  species  are  in  some  orders 
unfixed  and  in  process  of  formation.  There  is  no  better 
field  for  the  study  of  animal  variation,  and  the  problems 
imposed  upon  us  by  them  have  scarcely  begun  to  be 
appreciated. 


CHAPTER  II 

THEIR  RELATION  TO  PLANTS  AS  BENEFACTORS 

WHILE,  in  a  general  way,  insects  frequent  plants 
merely  to  feed  on  them,  yet  this  feeding  is  not  neces- 
sarily destructive  and  may  even  contain  an  element  of 
advantage.  Hence  we  find  that,  far  from  developing 
structures  to  repel,  many  plants  produce  attractive 
flowers  and  secrete  nectar  as  an  invitation  to  insects  to 
call  upon  or  visit  them. 

Flowering  plants  as  a  rule  have  two  kinds  of  sexual 
organs:  the  pistil  connected  with  the  seed  or  female 
element,  and  the  stamens,  producing  the  pollen  or  male 
element.  Fertilization  takes  place  when  the  pollen  or 
male  element  is  brought  into  contact  with  the  receptive 
surface  of  the  pistil,  and  this  pollination  may  be  produced 
in  many  different  ways.  Sometimes  the  same  flower 
has  both  pistil  and  stamens,  and  the  pollen  from  the 
latter  may  be  discharged  so  as  to  come  into  immediate 
or  direct  contact  with  the  former.  But  this  is  not 
always  the  case,  for  the  pistil  may  not  reach  the  recep- 
tive condition  until  after  all  the  pollen  has  been  removed 
from  the  stamens  and,  on  the  other  hand,  the  pistil 
may  become  receptive  before  the  pollen  on  the  same 
flower  is  mature.  In  such  cases  there  must  be  polli- 
nation by  some  outside  agency.  Many  flowers  are  of 
one  sex  only,  i.e.,  either  pistillate,  bearing  female 
organs  only,  or  staminate,  bearing  male  organs  only: 
and  sometimes  an  entire  tree  or  plant  may  bear  flowers 
of  one  sex  only.  Here  again  pollination  by  some  carrier 
is  necessary  and  among  the  carriers  the  most  active 
agents  are  the  wind  and  insects. 


22 


INSECTS 


Plants  which  depend  upon  the  wind  for  pollination 
usually  produce  a  light  pollen  in  great  quantity,  so  that 
at  times  the  air  may  be  full  of  it.  Plants  which  depend 
upon  insects  for  pollination  may  produce  much  or  little ; 
but  it  is  usually  somewhat  sticky  so  as  to  adhere  readily 
to  the  body  or  vestiture  of  the  visitor.  And  as  insects  are 
not  altruistic  enough  to  call  on  the  flowers  merely  to 
benefit  them,  some  sort  of  attraction  must  be  offered 


FIG.  5. — Section  through  a  flower,  illustrating  the  reproductive  parts. 

to  invite  the  visits.  This  attraction  may  be  in  the  shape 
of  honey  or  nectar  for  those  species  who  seek  for  them- 
selves alone,  or  for  their  progeny;  or  in  the  shape  of 
pollen  suitable  for  use  as  food  directly  or  in  preparing 
food  for  the  young  of  the  visitor. 

Where  nectar  alone  is  relied  upon  to  attract,  it  is 
usually  stored  so  as  to  compel  the  insects  to  come  into 
contact  with  the  reproductive  organs  in  their  efforts  to 
reach  it;  and  in  such  cases,  not  infrequently,  the  flowers 
are  modified  to  invite  special  kinds  of  insects  only. 


THEIR  RELATION  TO  PLANTS  23 

For  instance,  the  clovers  are  especially  adapted  to 
attract  long-tongued  bees;  flowers  like  the  Petunia, 
the  evening  primrose  or  the  jimpson  weed  attract  the 
hawk-moths,  whose  long,  flexible  tongues  reach  to  the 
nectar  cups  at  the  very  bottom  of  the  deep  florets. 


FIG.  6. — a,  Yucca  flower  with  moth  in  position,  ovipositing;  &,  Pronuba  gath- 
ering its  pollen  mass;  c,  head  of  Pronuba  from  side  showing  the  maxillary 
tentacle;  d,  tip  of  the  ovipositor. 

So  far  as  the  insects  are  concerned  the  pollination 
is  a  mere  incident  in  most  cases:  it  occurs  because  the 
flower  is  so  built  that  it  must  occur  when  the  pollen  or 
nectar  is  gathered.  But  there  is  at  least  one  case  in 
which  it  appears  almost  as  if  the  insect  acted  intel- 
ligently, with  a  definite  purpose  in  view,  and  the 
demonstration  of  this  case  we  owe  to  the  careful  obser- 


24  INSECTS 

vations  of  Dr.  C.  V.  Riley,  erstwhile  Entomologist  to 
the  U.  S.  Department  of  Agriculture. 

The  flowers  of  the  species  of  Yucca  are  absolutely 
incapable  of  self-  or  wind-pollination,  and  the  stigma  is 
so  situated  that  no  ordinary  insect  visitor  can  reach  it 
in  a  casual  search  for  food.  In  some  localities,  it  was 
observed  that  the  common  Yucca  or  soap-weed  never 
produced  seed  and  that  wherever  seed  was  produced, 
almost  every  pod  was  infested  by  a  little  caterpillar 
that  destroyed  a  greater  or  less  percentage  of  the  seeds. 
The  parent  of  this  caterpillar  is  a  small  white  moth, 
the  Pronuba  ynccasella  of  Riley,  in  which  the  mouth- 
parts  are  curiously  modified  and  utterly  unlike  those  of 
any  other  moth  species  that  we  know.  At  the  sides  of 
the  ordinary  tongue  there  are  developed  a  pair  of  flex- 
ible processes  set  with  little  pegs  and  spines,  and  capable 
of  being  coiled  like  the  tongue  itself.  When  the  female, 
which  alone  has  these  processes,  is  ready  to  lay  an  egg, 
she  enters  a  Yucca  blossom,  gathers  a  little  mass  of 
pollen,  rolls  it  into  a  ball,  carries  it  by  means  of  the 
coiled  processes  to  the  pistil,  and  rams  it  down  so  as 
to  bring  it  into  direct  contact  with  the  receptive  surface. 
Not  until  this  has  been  completed  does  she  turn  and 
then,  into  the  ovary  or  embyro  seed  pod,  she  forces  an 
egg  by  means  of  a  slender,  sharp-pointed  ovipositor. 
She  is  now  ready  to  repeat  the  process  on  another  flower 
and  she  does  repeat  it  until  her  stock  of  eggs  is  exhausted. 
Here  we  have  a  deliberate  pollination  preceding  ovi- 
position,  as  if  the  insect  knew  that  it  would  be  useless 
to  lay  an  egg  until  the  possibility  of  development  in 
the  seed  pod  was  assured. 

This  peculiarity,  though  confined  so  far  as  we  know 
to  the  genus  Pronuba,  is  not  confined  to  one  species 
only.  There  are  a  number  of  Yuccas  in  the  country, 
including  the  giant  or  tree  Yuccas  of  the  southwest, 


THEIR  RELATION  TO  PLANTS  25 

and  for  every  species  of  Yucca  there  is  a  species  of  Pro- 
nuba.  Surely  a  most  wonderful  adaptation  of  insect  and 
plant,  neither  of  which  can  now  exist  without  the  other. 

And  yet,  while  the  adaptation  is  not  so  specific,  nor 
the  evidence  of  design  so  apparent,  the  dependence  of 
red  clover  upon  long-tongued  bees  is  not  less  absolute. 
Australia  has  no  native  bumble-bee,  and  red  clover  was 
unknown  there  until  the  colonists  began  to  cultivate  it. 
There  was  no  difficulty  in  making  crops  of  forage;  but 
it  would  not  seed.  Importing  seed  annually  was  expen- 
sive and,  naturally,  the  Australians  were  anxious  to 
raise  their  own.  This  led  to  a  study,  of  the  reasons  for 
the  failure,  in  the  course  of  which  the  dependence  of  the 
plant  upon  bumble-bees  was  established.  The  remedy 
was  obvious,  and  now  European  bumble-bees  disport 
themselves  among  the  Australian  red  clover,  seed  is 
plentiful,  and  interference  with  bumble-bees  is  a  crime — 
as  it  should  be  rated  everywhere. 

Bees,  by  the  way,  are  the  most  universal  pollenizers, 
and  are  highly  specialized  for  that  purpose.  All  bees 
are  more  or  less  hairy:  sometimes  conspicuously  so,  a 
dense  woolly  clothing  appearing  all  over  the  body; 
sometimes  sparsely,  the  hair  being  often  localized.  But 
whatever  the  bee,  and  however  scant  its  clothing,  the 
hair  is  always  compound:  spurred,  branched  or  even 
plumose.  In  some  series  it  is  so  strikingly  characteristic, 
that  from  the  hair  alone,  the  genus  to  which  a  bee 
belongs  can  be  determined  with  reasonable  certainty. 
In  all  modifications  and  adaptations,  be  they  small  or 
great,  the  pollen-gathering  function  is  always  attained: 
for  bees  need  pollen  in  their  domestic  economy.  Most 
insect  mothers  have  no  more  care  for  their  offspring 
than  to  place  the  egg  in  some  position  where  the  larva, 
when  hatched,  will  find  food.  In  the  Hymenoptera,  to 
which  the  bees  belong,  storing  food  upon  which  the 


26  INSECTS 

larva  feeds  is  a  common  occurrence,  and  the  larva, 
when  hatched,  finds  surrounding  it  sufficient  nourish- 
ment to  bring  it  to  maturity.  In  the  social  forms, 
matters  have  developed  yet  further,  and  the  larva  does 
not  even  feed  itself:  it  is  fed  by  the  mother  or  a  nurse, 
and  its  food  is  prepared  beforehand;  either  a  mixture 
of  pollen  and  honey,  or  fragments  of  insects  mixed 
with  salivary  secretions  of  the  adult.  And  so  bees  need 
pollen  as  food  for  their  larvae,  and  upon  the  mothers  or 
females  falls  the  burden  of  gathering  and  storing  it. 
For  convenience  we  consider  as  females  those  sexually 
undeveloped  forms  in  the  social  species  which  we  know 
as  workers,  and  in  that  sense  all  the  female  bees  are 
supplied,  not  only  with  gathering  hairs,  but  with  some 
sort  of  structures  to  carry  the  pollen.  In  the  common 
hive-bee  the  inside  of  the  first  joint  of  the  hind  foot  or 
tarsus  is  modified  into  a  curry-comb-like  structure  for 
cleaning  the  pollen  grains  out  of  the  hair,  and  the  out- 
side of  the  hind  tibia  is  provided  with  a  fringe  of  long 
hair  forming  a  basket  into  which  the  pollen  is  packed 
for  transportation.  In  other  bees  other  parts  of  the 
legs,  of  the  breast,  or  even  of  the  abdomen  are  provided 
with  means  of  transporting  pollen  loads,  and  so  after 
a  visit  to  the  first  flower  the  bee  is  fitted  for  its  mission 
of  fructification,  which  occurs  as  a  mere  incident  in  the 
gathering. 

There  is  no  group  among  the  insects  that  is  more 
interesting  as  a  subject  for  study  than  that  containing 
the  bees.  Not  only  are  the  structures  of  adaptation 
very  beautifully  developed  for  their  purpose;  but  their 
life  history  is  often  of  intense  interest.  On  the  honey 
bee  alone  we  have  not  only  the  vestiture,  the  pollen 
carrier  and  the  brushes  that  clean  out  the  pollen  from 
the  hair;  we  have,  in  addition,  the  antenna-cleaner 
on  the  fore  leg  and  the  complicated  mouth  parts.  The 


THEIR  RELATION  TO  PLANTS 


27 


PIG  ^ — Bee  structures:  a,  honey  bee,  pollen  loaded;  b,  mouth  parts  of  a  long- 
tongued  bee;  c,  hind  leg  of  bee  showing  pollen  carrier;  d,  wax  cutter  and  curry- 
comb of  ist  joint  of  hind  tarsus;  e,  antenna-cleaner  of  fore  leg;  f,  hair  of  bumble- 
bee; g,  hair  of  Melissodes;  h,  hair  of  Megachile;  i,  hair  of  Xylocopa. 


28  INSECTS 

antenna-cleaner  is  a  little  notch  on  the  inner  side  of  the 
basal  joint  of  the  front  tarsus,  set  with  fine  teeth  and 
closed  by  a  spur  from  the  end  of  the  fore  tibia.  When 
the  bee  desires  to  comb  out  the  vestiture  of  one  of  the 
feelers,  the  fore  leg  is  brought  up,  the  notch  is  hooked 
over  the  stem  at  base,  the  spur  is  brought  to  the  lock, 
and  at  a  single  sweep  the  entire  series  of  joints  is  brought 
into  condition.  It  is  all  very  simple  and  very  neat, 
and  could  not  'be  better  adapted  for  its  purpose  if 
designed  by  man  himself.  The  mouth  structures  which 
are  also  kept  in  condition  with  this  apparatus  merit  a 
little  further  attention. 

I  have  already  alluded  to  "long-tongued"  bees  and 
this  has  carried  with  it  the  suggestion  that  there  was  a 
difference  in  that  respect.  As  a  matter  of  fact  there  is 
every  intermediate  form  between  the  tongue  of  the 
bumble-bee,  more  than  half  as  long  as  the  insect  itself, 
and  the  little  digger  bee,  whose  labium  or  lower  lip  does 
not  extend  beyond  the  edge  of  the  moutii.  It  is  not 
always  easy  for  the  novice  to  recognize  to  which  division 
a  bee  under  observation  belongs,  because  the  long  tongue 
is  usually  hinged,  and  may  be  drawn  back  against  the 
breast  in  such  a  way  as  to  be  protected  from  danger  of 
injury.  When  fully  extended  the  mouth  has,  laterally, 
a  pair  of  very  well-developed  mandibles,  which  usually 
serve  more  as  tools  in  building  homes  than  as  organs 
for  securing  food.  Between  these  mandibles,  and  com- 
pletely separated  from  them,  is  a  pair  of  sheath-like 
structures  which  are  generally  pointed  at  the  tip.  These 
are  the  maxillae,  which  are  not  of  much  active  use, 
though  they  are  the  organs  by  means  of  which  ripe 
grapes  and  other  fruits  are  occasionally  punctured 
when  normal  supplies  are  scarce.  In  the  very  centre  is 
the  flexible  tongue  itself,  ringed  in  structure,  with  series 
of  hairs  round  about  it,  and  a  little  button  of  hair  at  the 


THEIR  RELATION  TO  PLANTS  29 

tip.  This  is  the  structure  that  is  forced  down  into  the 
very  heart  of  the  flower  and  forms  a  lapping  organ,  by 
means  of  which  every  particle  of  nectar  may  be  secured. 
The  bee  is  not  really  a  sucking  insect  at  all;  but  gets  its 
food  by  lapping  somewhat  after  the  manner  in  which 
a  dog  laps  water. 

Only  the  honey  gatherers  have  tongues  of  this  type. 
Bees  and  honey  are  usually  associated,  but  as  a  matter 
of  fact  many  kinds  gather  no  honey  at  all,  and  very 
few  of  them  store  it.  In  the  species  in  which  there  is  no 
elongated  central  tongue,  this  is  replaced  by  a  short 
bladder-like  organ,  also  set  with  more  or  less  spatulate 
hair,  suited  for  lapping,  but  not  for  getting  down  into 
deep  flowers.  Bees  of  this  sort  we  find  on  our  shallow 
flowers  like  those  of  the  strawberry,  blackberry  and 
other  Rosace®,  and  many  of  these  gather  no  honey  at  all. 

It  is  a  delightful  pastime,  although  not  always  easy, 
to  investigate  the  domestic  economy  of  the  various 
bees.  Some  of  them  make  nests  or  cells  of  mud  gathered 
from  road-side  puddles;  some  bore  into  twigs,  branches 
or  even  boards  and  in  the  tunnels  so  chewed  out  form 
the  cells  in  which  a  brood  is  raised;  some  make  cells  of 
wax  in  cavities  of  trees;  others  seek  a  cavity  under  the 
turf,  and  in  a  mass  of  pollen  raise  their  brood  with  little 
attempt  at  making  cells  of  any  kind;  and  yet  others 
dig  down  deep  underground,  five  or  six  feet  below  the 
surface  and,  far  from  the  light,  build  the  homes  in  which 
their  young  are  developed.  And  when  we  find  a  bee- 
home,  we  can  always  recognize  it  by  the  character  of 
its  store.  It  may  be  a  cake  of  solid  pollen,  packed  hard 
in  a  definite,  loaf- like  form,  or  it  may  be  a  semi-liquid 
mass  of  mixed  pollen  and  honey,  so  arranged  that  the 
larva  may  feed  on,  without  being  imbedded  in,  it.  But 
always  there  is  pollen,  and  the,  pollen  gatherer  is  always 
also  a  plant  fructifier. 


INSECTS 


There  are  many  others  among  the  Hymenoptera 
that  are  useful  in  the  work  of  pollination  because  of 
their  habit  of  feeding  among  the  flowers,  even  if  not  on 
them;  but  all  this  is  based  on  the  same  visits  which  the 
flower  encourages  and  of  which  it  takes  advantage; 

but  no  account  of  this  sort 
of  relationship  could  be  con- 
sidered even  passably  com- 
plete, without  some  reference 
to  the  complicated  relation- 
ship existing  between  the 
Smyrna  fig  and  the  minute 
little  Blastophaga,  a  species 
whose  life  relations  have  been 
beautifully  worked  out  by  the 
Entomologists  of  the  United 
States  Department  of  Agri- 
culture. 

The  Smyrna  fig  of  com- 
merce depends  for  its  edible 
quality  upon  the  ripened 
seeds  that  it  contains.  The 
fig  is  not  really  a  true  fruit 
as  that  term  is  generally 
defined,  but  is  a  thick  fleshy 
envelope  within  which  the 
flowers  are  contained.  In 
the  Smyrna  fig  these  flowers 

are  all  female  and  no  pollen  is  produced  anywhere  on 
the  tree.  Left  to  themselves,  such  trees  could  never 
produce  ripe  fruit,  and  that  was  the  condition  of  the 
Smyrna  fig  orchards  in  California,  prior  to  1900.  In  the 
Mediterranean  countries,  whence  our  commercial  sup- 
ply is  generally  derived,  there  are  found  beside  the  culti- 
vated also  several  varieties  of  wild  or  caprifigs,  which 


FIG. 8.— a,  cell  of  Augochlorawith 
egg  laid  on  pollen  mass;  b,  cell  of 
Andrenid  with  egg  resting  on  mix- 
ture of  pollen  and  honey;  c,  cells  of 
carpenter  bee  in  wood;  d,  mud  cells 
of  mason  bee  in  burrow — c  and  d, 
after  Packard. 


THEIR  RELATION  TO  PLANTS  31 

produce  three  crops  of  fruit  during  the  season.  These 
fruits  contain  male  flowers,  producing  an  abundance  of 
pollen;  but  this  pollen  is  never  naturally  discharged 
from  the  envelope  containing  the  florets. 


FIG.  9. — Blastophaga  pollenizer  of  fig:   a,  female;   b,  c,  male  in  two  positions. 


Yet  it  was  recognized  by  the  fig-growers  in  the 
Orient  that  to  obtain  fruit  of  the  commercial  edible 
varieties,  it  was  necessary  to  bring  to  them  when  in 
bloom,  branches  containing  fruit  of  the  caprifig,  which 


32  INSECTS 

were  usually  hung  up  in  the  tree  which  it  was  intended 
to  fructify.  This  work  of  pollination  is  accomplished 
by  the  Blastophaga  already  referred  to,  although,  far 
from  benefiting  itself  in  the  process,  the  insect  dies 
without  even  being  able  to  continue  its  kind. 

In  the  caprifigs  the  female  flowers  are  replaced  by 
little  gall-like  swellings  in  which  the  larvae  of  the  Blasto- 
phaga develop.  One  generation  of  figs,  the  so-called 
"mammae,"  remain  on  the  trees  during  the  winter  and 
by  the  time  they  are  ready  to  drop,  there  is  already  on 
the  trees  a  new  or  spring  crop  of  fruit,  known  as  the 
"profichi. "  By  the  time  that  this  crop  is  in  proper 
condition,  the  insects  that  have  hibernated  in  the 
"mammae,"  are  fully  developed,  the  wingless  and  almost 
blind  male  Blastophaga  has  fertilized  the  female  before 
she  is  even  out  of  her  cell,  and  the  latter,  leaving  the 
dried-up  fig  by  the  small  anterior  opening,  makes  its 
way  into  the  new  figs,  to  provide  for  a  new  generation. 
In  the  "profichi"  this  generation  matures  at  the  time 
the  commercial  Smyrna  fig  is  in  proper  condition  and 
the  females,  emerging  pollen  covered  from  the  "pro- 
.  fichi,"  enter  the  small  opening  of  this  true  female  flower 
receptacle,  if  they  find  themselves  in  a  tree  bearing  them. 
But  in  this  Smyrna  covering  all  the  female  florets  are 
fully  developed,  and  the  gall-like  swellings  that  replace 
them  in  the  caprifigs  are  absent.  The  insect  therefore 
moves  about  over  the  entire  interior  surface  of  the 
pouch,  seeking  a  place  to  oviposit,  and  in  the  process 
distributes  its  load  of  pollen  everywhere.  It  event- 
ually dies  without  reproducing,  and  usually  without 
even  being  able  to  make  its  way  out  again.  But 
though  the  insect  has  lost  its  life,  the  tree  has  gained 
and  the  seed  pouch  that  we  know  as  the  fig,  comes  to 
maturity  and  ripens  seed. 


THEIR  RELATION  TO  PLANTS  33 

At  the  same  time  that  the  Smyrna  fig  which  produces 
the  edible  commercial  fruit  is  in  bloom,  there  is  also 
another  crop  developing  on  the  caprifigs,  and  these  are 
known  as  "mammoni. "  The  Blastophaga  issuing  from 
the  "profichi"  on  the  same  tree,  naturally  enter  these 
fruits  which  are  of  the  same  character  as  the  preceding 
crops,  and  are  able  to  continue  their  kind,  coming  to 
maturity  when  the  third  crop  is  ready  for  their  reception. 
This  third  crop  represents  the  "mammae"  or  over- 
wintering form,  from  which  the  "profichi"  of  the  fol- 
lowing season  are  again  entered  by  the  Blastophaga. 

Here  we  have  an  extremely  complicated  relation- 
ship which,  reduced  to  its  simplest  terms,  means  that 
in  order  to  produce  the  commercial  Smyrna  fig  there 
must  be  suitable  caprifigs  producing  "profichi"  infested 
by  Blastophaga,  at  a  period  corresponding  to  the  develop- 
ment of  the  female  flower  capsule.  And  as  the  insects 
are  very  small  and  very  frail,  the  caprifigs  must  be 
either  well  distributed  among  the  Smyrna  trees,  or  the 
infested  "profichi"  must  be  gathered  and  distributed 
among  the  trees  to  be  pollenized. 

The  accounts,  published  by  Dr.  L.  O.  Howard  in  the 
Bulletins  and  Reports  of  the  U.  S.  Department  of 
Agriculture,  make  interesting  reading  and  show  how, 
after  many  trials  and  much  painstaking  investigation, 
the  Blastophaga  and  the  necessary  caprifigs  were  finally 
introduced  into  the  fig-growing  districts  of  California, 
and  how  a  new  industry,  absolutely  depending  for  its 
continuance  upon  a  minute  hymenopterous  insect,  was 
finally  established  upon  a  firm  and  scientific  basis. 

How  many  cases  of  this  kind  exist  among  plants 
having  no  present  economic  value  it  would  be  difficult 
to  estimate,  and  how  so  complicated  a  relationship  ever 
became  established  is  not  yet  explainable  even  by  a 
theory. 
3 


34  INSECTS 

The  Lepidoptera  have  been  already  incidentally 
referred  to  as  pollenizers  and  they  rank,  as  an  order, 
next  to  the  Hymenoptera  in  importance.  Butterflies 
and  moths,  when  they  feed  at  all,  feed  only  on  liquids 
and  most  of  them  on  prepared  plant  juices  or  nectar. 
The  butterfly  hovering  over  a  flower  and  sipping  honey, 
is  a  familiar  figure,  and  the  visits  of  hawk-moths  to  the 
flowers  that  open  at  dusk  are  fairly  well  known;  but 
that  busy  life  that  stirs  among  the  flowers  after  night 
falls,  is  unknown  except  to  the  naturalist  who  prowls 
about  in  wood  and  field,  among  the  hedges  and  along 
the  road,  often  with  a  bulls-eye  lantern  like  a  thief; 
seeking  indeed  to  surprise  some  of  nature's  secrets  by 
artificial  light,  his  organs  of  sight  being  far  inferior  to 
those  of  the  creatures  whom  he  seeks  to  study. 

That  many  flowers  are  most  fragrant  at  night,  and 
that  many  fragrant,  night-blooming  flowers  are  white 
•or  without  striking  colors,  is  a  commonplace  to  one 
who  knows  the  country  at  all;  but  that  this  penetrating, 
fragrance  is  to  attract  insect  visitors  at  a  time  when  sight 
does  not  suffice  for  an  invitation  is  not  so  well  known. 
And  yet  it  is  at  night  that  the  most  abundant,  albeit 
almost  noiseless,  life  can  be  observed  on  such  flowers, 
and  here  we  will  find  owlet  and  other  moths  busily 
engaged  in  probing  every  floret  and  incidentally  accom- 
plishing nature's  aim  of  reproduction.  I  say  "inci- 
dentally" with  intent  in  this  case,  because  neither 
moth  nor  butterfly  has  any  use  for  the  pollen  that  it 
dislocates  and  relocates  as  it  moves.  It  is  after  food, 
purely  and  simply,  and  that  food  is  nectar:  if  in  reaching 
that  nectar  the  tongue,  pollen  laden,  is  brought  into 
contact  with  the  stigma,  that  is  merely  because  the 
insect  could  not  help  itself,  any  more  than  it  could  pre- 
vent the  adhesion  of  a  few  grains  of  pollen  from 
another  flower. 


THEIR  RELATION  TO  PLANTS 


35 


Exceptions  occur  always  and  that  of  Pronuba  in  its  re- 
lation to  Yucca  has  been  related ;  but  in  general  the  Lepi- 
doptera  pollenize  as  a  mere  incident  and  with  the  tongue, 
while  feeding.  And  this  tongue  is  a  really  interesting  bit 
of  structure.  It  is  coiled  like  a  watch  spring  when  at  rest 
between  the  mouth  feelers,  and  no  one  would  suspect. its 
presence  or  size  from  an  ordinary  dried  specimen;  but 
when  uncoiled  it  is  often  as  long  and  sometimes  much 
longer  than  its  bearer,  and  here 
again  we  have  that  beautiful 
ringed  structure  that  adapts  it- 
self to  so  many  purposes  among 
the  insects.  There  is  no  flower 
so  deep  that  its  nectaries  are 
beyond  the  reach  of  all  insects 
but  there  are  many  flowers  so 
deep  that  only  a  single  long- 
tongued  species  is  invited.  And 
therefore  we  have  an  abun- 
dance of  species  with  tongues 
of  less  than  an  inch  in  length, 
quite  a  number  that  have  them 
from  two  to  four  inches  and 
a  very  few  where  ten  or  even 
twelve  inches  are  attained. 

The  butterfly  tongue  really  consists  of  two  separate 
parts  or  halves,  the  modified  maxillae,  held  together 
by  specially  developed  structures;  and  the  space  be- 
tween them  forms  the  tube  through  which  the  liquids 
are  carried  into  the  mouth.  Each  half  contains  its 
own  supply  of  muscles,  a  large  tracheal  tube  extends 
to  the  very  end,  and  there  is  an  excellent  supply  of 
nerve-fibres  to  guide  the  insect  in  its  operations  in  the 
depths  of  the  florets. 

Most  of  the  tongue  is  bare  or  set  with  scanty  stiff 


FIG.  10. — a,  tip  of  butterfly 
tongue  showing  the  sensory  pits 
and  taste  cups ;  b,  section  through 
tongue  showing  division  into  two 
halves. 


36  INSECTS 

hair  only;  but  at  the  tips  in  the  different  species,  are 
found  a  great  variety  of  tactile  structures,  taste  cups 
and  gathering  processes,  by  means  of  which  our  moth 
not  only  recognizes  the  presence  of  something  good  to 
eat,  but  manages  to  get  it  all,  as  well.  In  the  adult  stage 
as  moths  or  butterflies,  the  Lepidoptera  have  few  bad 
and  many  good  qualities;  but  in  the  larval  or  cater- 
pillar stage  the  reverse  is  the  case.  As  pollenizers  the 
Lepidoptera  could  be  missed  much  more  readily  than  the 
bees;  none  of  our  cultural  plants  depending  upon 
them  for  their  continued  existence. 

Among  the  Coleoptera  or  beetles  there  are  many 
that  frequent  flowers  for  one  purpose  or  another  and 
many  of  these  are  more  or  less  pubescent  or  covered 
with  hair,  so  that  they  may  be  and  often  really  are 
much  covered  by  pollen  as  they  move  about.  And 
as  they  move  about  they  do  without  question  add 
their  share  to  plant  fruitfulness ;  but  they  are  also  very 
often  feeders  upon  them  or  upon  the  pollen.  In  so 
far  as  they  are  pollen-feeders  merely,  this  does  little 
harm,  because  that  is  usually  produced  in  great  ex- 
cess; but  some  feed  on  the  pollen  in  such  a  way  as  to 
rob  the  plant  of  all  possible  chance  of  benefit.  For 
instance  the  strawberry-weevil  in  the  larval  stage 
subsists  altogether  upon  pollen.  But  the  parent  beetle 
punctures  the  unopened  bud,  lays  the  egg  in  the  mass 
of  forming  pollen  and  then  punctures  the  stalk  below 
the  bud,  so  that  the  latter  may  never  open.  This  is 
sheer  robbery  without  corresponding  benefit  and,  on  the 
whole,  flowers  pay  pretty  heavily  for  such  incidental 
advantages  as  they  derive  from  the  visits  of  beetles.  In 
any  case  the  pollination  is  purely  incidental,  for  the 
beetles  gather  neither  pollen  nor  honey,  and  the  hairy 
covering  is  not  modified  to  make  it  especially  serviceable 
as  a  carrier. 


THEIR  RELATION  TO  PLANTS  37 

Diptera  or  flies  are  often  intimately  associated 
with  flowers,  and  many  of  these  are  hairy,  some  even 
with  spurred  or  compound  hair;  but  none  with  modi- 
fications that  adapt  them  especially  or  peculiarly  as 
pollenizers.  We  have  one  family,  the  BombyliidtB  or 
bee-flies,  resembling  bumble-bees  somewhat  in  appear- 
ance and  quite  as  hairy,  many  of  which  also  have  a 
long  tongue  rivalling  some  of  the  Lepidoptera.  But 
their  habits  are  quite  different.  One 
never  sees  them  buried  in  a  flower 
or  rolling  about  among  the  blos- 
soms, pollen-covered.  On  the  con- 
trary they  usually  hover  daintily  over 
bare,  sandy  areas  or,  if  over  flowers, 
then  very  delicately  and  resting 
lightly  when  at  all.  That  they  are 
of  some  use  to  the  plants  is  prob- 
able; but  they  have  no  important 
function.  And  the  same  is  true  of  FIG.  n.— chrysanthe- 

c^         j   .  j          .  -i  f  .,  mum  fly ;  Eristalis  tenax. 

the    Syrphida    that    are    found    so 

often  resting  on  or  about  blooms: 

the  majority  of  these  are  bare,  or  have  only  a  thin  soft 

vestiture    and    slender    hairless    legs    to    which    pollen 

could  not  adhere  if  it  would. 

An  exception  to  this  general  statement  is  found  in 
the  chrysanthemum  or  "drone  fly,"  a  burly  bustling 
species  that  becomes  conspicuous  late  in  the  season 
and  resembles  in  size,  color  and  general  appearance  a 
honey  bee,  for  which  indeed  it  is  often  mistaken.  A 
little  experience,  however,  shows  that  it  has  no  sting, 
and  therefore  the  term  "  drone  fly  "  is  not  so 
inappropriate. 

Growers  of  chrysanthemums  believe  this  fly  of 
great  importance  in  the  pollination  of  that  plant  and 
they  may  be  correct;  but  on  other  plants  or  flowers 


38  INSECTS 

they  are  of  little  use.  Their  habits  in  the  early  stages 
are  about  as  unlike  those  of  the  adults  as  it  is  easily 
possible  to  imagine.  The  larvae  live  in  all  sorts  of  semi- 
liquid  excrementitious  matter  and  are  known  as  rat- 
tailed  maggots,  because  of  the  long  anal  process  by 
means  of  which  they  obtain  air  from  above  the  surface 
of  the  filthy  mess  in  which  they  live. 

The  number  of  flies  known  to  us  is  already  very 
great,  and  the  number  that  still  remains  to  be  studied 
is  probably  even  greater;  while  as  to  their  habits  we 
know  them  in  the  most  general  way  only.  There  may, 
therefore,  be  groups  more  decidedly  beneficial  to 
plants  than  anything  that  I  have  mentioned;  but 
there  can  be  nothing  comparable  with  the  bees,  since 
none  of  the  flies  store  food  for  their  progeny. 

The  fact  is,  then,  that  many  plants  depend  for  their 
reproduction  entirely  upon  insect  visitors.  Some  flowers 
are  so  constructed  that  only  very  specialized  forms  can 
accomplish  the  function  of  pollination  and  there  is  in 
many  such  cases  a  mutual  dependence:  the  insect  can- 
not exist  without  the  plant  nor  can  the  plant  continue 
its  kind  without  the  insect.  Other  flowers  issue  a  general 
invitation  by  bright  colors,  wide  open  parts,  abundant 
pollen  or  filled  nectaries,  readily  accessible  to  anything 
that  may  come  along.  Yet  others  depend  upon  nectaries 
that  are  attractive,  but  are  so  situated  that  any  insect 
that  succeeds  in  gaining  access  to  them  must  of  necessity 
pay  in  pollenizing.  And  here  we  come  to  a  subject  on 
which  the  botanist  has  his  say,  and  shows  how  ingenious 
are  some  of  these  plant  structures  and  how  well  adapted 
to  their  end,  so  that  pollination  may  even  be  accom- 
plished without  the  necessity  for  bringing  the  pollen 
into  contact  with  the  insect  at  all,  the  latter  merely 
releasing  the  trigger  that  restrains  the  distribution  of 
the  fructifying  material. 


THEIR  RELATION  TO  PLANTS 


39 


There  is  one  other  method  in  which  insects  are 
useful  to  plants,  and  that  is  as  food.  A  very  few  plants 
are  "carnivorous"  or  feed  upon  animal  food,  and  that 
animal  food  consists  mostly  of  insects;  but  that  is  a 
relation  which  is  extremely  simple  in  character  al- 
though the  plant  habit  is  exceptional. 


CHAPTER  III 

THEIR  RELATION  TO  PLANTS  AS  DESTROYERS 

WHILE,  as  has  just  been  shown,  there  is  a  mutual 
interdependence  of  plants  and  insects  in  which  both 
may  be  benefited,  or  if  one  is  harmed,  the  benefit 
derived  is  so  far  in  excess  of  the  injury  suffered  that  it 
does  not  count  against  the  value  of  the  relation,  there 
is  also  a  kind  of  dependence  in  which  the  insect  gets 
all  the  benefit,  and  the  plant  all  the  injury. 

A  vast  number  of  insects  depend  absolutely  upon 
plants  for  their  very  life  and  give  nothing  at  all  in  re- 
turn: they  are  destroyers  pure  and  simple,  using  the 
plant  tissue  as  food,  as  material  to  supply  protection, 
or  as  a  habitation.  But  the  amount  and  character  of 
the  injury  vary  enormously  and  may  either  be  a  neg- 
ligible incident  in  the  life  of  the  plant,  or  form  the 
principal  check  to  its  growth  or  cultivation. 

We  may  dismiss  with  no  more  than  a  mere  mention 
that  vast  horde  of  insects  that  gets  into  plants  when 
they  are  dead  and  begin  to  disintegrate.  Nature  dis- 
likes dead  organic  matter,  and  when  a  tree  or  plant 
is  dead  or  dying,  or  when  decay  begins  in  a  sappy  fruit 
or  fungus,  there  are  insects  among  other  agents  ready 
to  reduce  it  to  that  inorganic  condition  from  which  it 
originated.  While  the  actual  death  of  a  diseased  or 
weakened  tree  is  often  hastened  by  such  insects,  they 
can  hardly  be  said  to  be  enemies  in  the  direct  sense ;  but 
scavengers,  ever  ready  to  begin  their  office  and  fostering 
the  condition  in  which  it  becomes  their  legitimate  prey. 

Beginning  with  the  simplest  order,  the  Thysanura, 
we  find  few  plant  destroyers  among  them.  Originating 

40 


THEIR  RELATION  TO  PLANTS  41 

as  they  did  in  primitive  times  when  dampness,  mud 
and  ooze  were  prevailing  conditions  and  vegetable 
life  just  established,  they  were  fitted  to  live  and  gain 
their  subsistence  in  disorganized  tissue:  they  were 
simple  forms  of  scavengers,  and  so  they  are  to-day  in 
most  cases.  They  are  always  found  where  there  is 
moist  vegetable  decay  and  sometimes,  in  manure  beds, 
they  occur  in  countless  numbers.  In  fermenting  sap, 
under  bark  of  trees  undergoing  moist  decay,  in  masses 
of  leaves  and  similar  localities,  these  species  may  gen- 
erally be  sought.  Their  direct  influence  upon  growing 
vegetation  is  extremely  small. 

In  the  Neuroptera  there  has  been  an  advance,  al- 
though, as  these  were  also  primitive  species  and  largely 
adapted  to  aquatic  or  semi-aquatic  life,  the  vegetable 
feeders  are  in  the  minority.  Almost  everywhere  the 
larval  life  is  more  or  less  predatory  in  tendency  and 
in  some,  like  the  Odonata  or  dragon  flies,  this  predatory 
character  is  carried  into  the  adult  stage.  The  feeders 
on  vegetable  matter,  like  Psocids  and  Termites,  usually 
attack  dry  or  dead  tissue  or  feed  upon  Lichens  and 
similar  material.  None  of  them  rank  as  destroyers  of 
the  higher  forms  of  plant  life,  although  Termites  do  in 
some  instances  attack  growing  vegetation. 

In  the  Hemiptera  we  have  a  well-developed  series 
of  terrestrial  species,  the  vast  majority  of  which  are 
feeders  on  plant  life  or  on  plant  juices  drawn  from 
living  plants.  The  mouth  structure  of  the  insects  is 
such  that  they  can  feed  only  on  the  liquid  which  they 
draw  from  a  punctured  tissue,  whether  vegetable  or 
animal,  and  therefore,  primarily,  the  injury  is  due  to 
a  withdrawal  of  sap,  severe  in  proportion  to  the  amount 
of  liquid  thus  withdrawn.  Secondarily,  injury  is  caused 
by  an  interruption  of  the  circulation  in  the  plant,  due 
to  a  hardening  of  the  exhausted  tissue,  or  the  drying 


42  INSECTS 

out  of  the  cells  from  which  the  liquid  matter  has  been 
abstracted.  More  rarely  a  positive  poisoning  of  the 
tissue  occurs,  due  apparently  to  the  injection  into  it 
of  the  salivary  secretion  of  the  insect,  and  this  may 
result  in  the  death  of  all  that  portion  of  the  plant  be- 
yond the  puncture.  That  sort  of  injury  is  often  pro- 


PIG.  12. — Mouth  parts  of  a  plant  louse — a,  the   jointed   beak;  b,  the 
lancets;   c,  the  feeler;    d,  the  foot. 


duced  on  succulent  plants  like  the  Cucurbs,  including 
cucumbers,  melons  and  the  like,  or  Solanacea,  includ- 
ing potatoes,  tomatoes,  egg-plants,  etc.,  the  offenders 
being  mostly  plant  bugs  of  the  families  Capsidce,  Lyg- 
(zidaz  or  Coreidcs. 

Plant  lice  are  universally   distributed  and  there  is 
scarcely  a  plant  not  in  some  way  subject  to  their  attacks. 


THEIR  RELATION  TO  PLANTS  43 

They  are  insignificant  as  individuals;  but  dangerous 
in  hosts:  and  hosts  grow  out  of  individuals  in  an  in- 
credibly short  time,  owing  to  their  fecundity.  Given 
a  few  eggs  on  the  tip  of  an  apple  twig  in  winter,  they 
hatch  into  young  lice  as  soon  as  the  leaf-buds  open 
and,  in  a  week  or  ten  days,  depending  upon  weather 
conditions,  these  begin  to  bear  living  young.  All  the 
specimens  hatching  from  the  winter  eggs  are  parthen- 
ogenetic  females;  i.e.,  females  which  do  not  require 
to  be  mated  with  a  male  before  reproducing  their  kind; 
and,  when  once  reproduction  begins,  it  is  in  the  nature 
of  a  continuous  performance;  four,  six,  eight  or  more 
young  being  produced  in  a  day  and  for  several  days  in 
succession.  Long  before  this  stem-mother  has  reached 
her  limit  of  increase,  the  first-born  daughters,  partheno- 
genetic  like  herself,  have  in  turn  begun  the  task  of 
multiplication  so  that,  by  the  time  the  leaves  are  fully 
formed,  the  surfaces  are  covered  by  plant  lice,  and  in- 
stead of  unfolding  and  reaching  full  size,  they  are 
curled,  twisted  and  crippled,  forming  an  unsightly 
mass  instead  of  a  beautifully  unfolded  cluster  or  tuft. 
And  now  we  are  apt  to  get  a  secondary  effect  due  to 
a  peculiarity  in  feeding.  Not  content  with  absorbing 
only  enough  to  sustain  life  and  to  reproduce,  the  insects 
gorge  continuously  and,  when  incapable  of  containing 
more,  they  eject  through  the  anus  a  stream  of  a  clear 
sweetish  liquid,  known  as  honey -dew.  It  was  cur- 
rently believed  that  the  two  tube-like  structures  near 
the  end  of  the  abdomen  were  the  chief  organs  through 
which  this  honey-dew  is  excreted  and  they  are  there- 
fore popularly  known  as  "honey-tubes":  more  technic- 
ally they  are  termed  cornicles,  which  conveys  no  opinion 
as  to  their  function.  This  honey-dew  drops  upon  the 
leaves  below,  often  in  such  abundance  as  to  form  a 
complete  coating  and  that,  in  turn,  is  an  excellent 


44  INSECTS 

culture  medium  for  a  soot  fungus  which  forms  a  black 
covering -that  disfigures  if  it  does  not  kill  the  foliage  or 
fruit.  It  goes  without  saying  that  what  is  true  of  the 
apple,  which  I  have  chosen  for  an  illustration,  is  equally 
true  of  the  cherry,  the  maple,  the  orange,  lemon  or  any 
other  tree  or  plant  subject  to  the  attacks  of  plant  lice  or 
others  of  their  allies  also  producing  honey-dew — mealy 
bugs,  white-fly,  Psyllids  and  even  some  scales. 


FIG.   13. — The  apple  louse:   b,  stem-mother;  a,  winged  parthenogenetic  form; 
c,  adult  male;    d,  winter  eggs  on  twig. 


To  return,  however,  to  our  stem-mother  on  the 
apple,  whom  we  left  engaged  in  the  task  of  increasing 
her  kind.  She  was  born  without  wings  and  never 
acquires  them,  and  her  daughters  are  like  her  in  this 
respect.  But  after  the  second  generation  matters 
become  crowded,  and  unless  relief  is  somehow  obtained 
there  will  be  more  than  can  be  maintained  on  the  orig- 
inal tree.  And  so  in  the  third  and  later  generations  a 


THEIR  RELATION  TO  PLANTS  45 

variable  number  of  individuals  develops  further  and 
becomes  winged.  There  is  not  in  this  case  any  genera- 
tion in  which  all  the  individuals  are  winged,  although 
there  are  species  in  which  such  a  condition  exists.  It 
is  simply  that  out  of  a  dozen  individuals  born  of  the 
same  mother  on  the  same  day,  a  number  develop 
wings  and  fly  away  to  other  trees  or  plants.  They  are 
no  further  advanced,  sexually,  than  the  stem-mother 
and  when  they  reach  their  new  homes  they  also  pro- 
duce living  young,  which  may  become  winged  or  re- 
main wingless;  and  this  sort  of  reproduction  continues 
until  the  end  of  the  season  and  the  gradual  decrease 
of .  sap  in  the  trees  and  plants  forces  a  provision  for 
winter  rest.  Late  in  the  fall,  therefore,  a  generation  is 
produced  in  which  both  sexes  are  represented  and 
from  a  union  of  these  the  winter  egg  is  produced. 

Now  while  this  in  a  way  epitomizes  the  usual  his- 
tory of  plant  lice,  there  is  an  infinite  amount  of  varia- 
tion. A  species  that  is  confined  to  one  tree  or  similar 
food  plant  may  do  very  well  without  much  modifica- 
tion; but  a  species  which  feeds  during  the  summer  on 
a  plant  that  dies  down  completely  before  winter,  needs 
some  provision  that  enables  it  to  continue  its  kind 
elsewhere;  hence  we  have  migrations  in  early  summer 
from  and  in  late  fall  to  the  winter  host.  In  a  melon 
field,  for  instance,  there  may  not  be  a  plant  louse  until 
the  vines  are  well  developed:  then  on  some  warm, 
almost  windless  day  in  June,  the  air  will  be  found  full 
of  drifting,  winged  aphids  and  next  day  a  sprinkling 
of  them  may  be  noted  all  over  the  melons,  giving  rise 
to  the  summer  generations  which,  in  late  fall,  again 
produce  return  migrants  that  find  their  way  to  plants 
upon  which  they  can  pass  the  winter.  Sometimes 
there  seems  to  be  a  direct  relationship  between  two 
plants,  as  apple  and  wheat  for  one  form  of  Aphid  that 


46  INSECTS 

attacks  both,  or  between  the  plum  and  the  hop,  where 
the  insect  cannot  exist  unless  both  its  alternate  hosts 
are  present.  At  other  times,  as  in  the  case  of  the  melon- 
louse,  the  insect  has  a  variety  of  food  plants  and  the 
migration  is  not  essential  to  the  continuance  of  the 
species.  In  fact  it  is  not  even  necessary  for  all  plant 
lice  to  go  into  the  egg  stage,  for  some  species  winter  as 
parthenogenetic  females  on  plant  remnants  or  on  stools 
like  the  rosettes  of  cruciferous  plants.  In  tropical  coun- 
tries the  resting  stage  is  often  during  the  dry  season, 
when  vegetation  has  little  spare  moisture. 

Some  species  attack  only  the  roots  of  plants,  and 
these  are  usually  wingless,  and  often  without  honey- 
tubes  or  cornicles.  Some  inhabit  the  roots  at  one 
season  and  the  leaves  at  another,  the  winter  being 
usually  spent  underground,  while  a  large  part  of  the 
growing  period  may  be  passed  on  the  foliage,  the  spread 
of  the  species  being  provided  for  there.  Such  species 
may  be  very  little  modified,  like  the  black  species  that 
occurs  on  peach,  or  very  greatly  specialized  like  the 
Phylloxera  that  occurs  on  grape,  and  is  so  great  a 
factor  in  all  countries  where  the  vine  forms  an  impor- 
tant part  of  the  agricultural  product.  This  Phylloxera 
vastatrix  winters  on  the  roots  as  a  partly  grown,  wing- 
less form.  It  grows  rapidly  in  spring  and  lays  eggs, 
the  young  from  which  are,  like  their  mothers,  wingless 
and  parthenogenetic,  laying  eggs  and  producing  others 
like  them  in  turn  throughout  the  season,  always  from 
unfertilized  eggs.  In  most  localities,  about  midsummer, 
some  specimens  acquire  wings,  work  their  way  to  the 
surface  and  fly  to  other  vines,  thus  providing  for  the 
rapid  spread  of  the  species.  These  winged  forms  lay 
from  three  to  eight  eggs  on  the  leaves,  some  of  them 
large,  producing  females,  the  others  small,  producing 
males.  These  sexed  forms  seem  to  be  produced  only 


THEIR  RELATION  TO  PLANTS 


47 


for  the  purpose  of  renewing  the  vitality  of  the  species 
for  they  are  without  wings,  incapable  of  flight  and  with- 
out mouth  parts,  incapable  of  feeding.  They  are 


FIG.  14. — Phylloxera  vastatrix — a,  sound  grape  rootlets;  b,  rootlets  with  newly 
formed  galls;  c,  same  with  old,  dried  up  tissue;  dd,  groups  of  lice  on  roots  and 
rootlets;  e,  f,  female  pupa,  above  and  beneath;  g,  h,  winged  females;  «,  antenna; 
j,  oviparous  wingless  female  and  her  eggs;  k~,  root  showing  location  of  the  eggs. 

sexually  mature  when  born,  copulate  soon  afterward, 
and  each  female  produces  one  egg  which  hatches  into 
a  form  similar  to  that  which  started  the  cycle  in  spring. 
But  the  winged  form  is  not  essential  for  this  renewal, 


48  INvSECTS 

for  at  any  time  during  the  summer  the  underground 
forms  may  lay  eggs  of  two  sizes  producing  similar  sexed 
forms  that  act  precisely  as  did  those  above  ground. 
So,  some  of  the  parthenogenetic  forms  may  leave  the 
roots  and  crawl  up  the  stem  to  the  foliage,  where  their 
progeny  form  those  characteristic  galls  which  strike  ter- 
ror into  the  heart  of  the  European  viticulturist,  while 
they  are  frequently  not  even  recognized  by  the  vine- 
grower  of  the  eastern  United  States.  Nor  is  this  leaf- 
form  a  necessary  feature  in  the  cycle  and  it  does  not 
occur  in  all  localities,  so  that  outward  indications  of 
Phylloxera  infestation  may  be  completely  lacking  ex- 
cept in  the  condition  of  the  vine.  The  Phylloxera  are 
gall-makers  as  a  rule,  and  on  the  roots  of  grape  pro- 
duce swellings  and  distortions  which,  on  vines  not 
accustomed  to  them,  result  in  the  death  of  the  roots 
or  serious  disturbance  in  function,  so  that  the  vines 
sicken  and  may  die.  In  the  original  home  of  the  species 
in  eastern  North  America  no  especial  injury  is  caused; 
on  the  Pacific  Coast  injury  may  be  severe,  but  the 
insect  does  not  spread  readily,  and  so  its  march  may 
be  checked;  while  in  European  countries  the  native 
vines  succumb  very  easily  to  the  attack  of  the  insect 
and  its  spread  is  rapid  where  energetic  measures  for 
its  destruction  are  not  resorted  to. 

There  are  other  species  of  plant  lice  producing  galls: 
some  on  hickory  make  bladder-like  structures  of  con- 
siderable size,  and  others  produce  ridges  aptly  com- 
pared to  a  cock's  comb,  on  elm.  In  fact,  from  the 
simple  distortion  produced  by  a  feeding  along  the  veins 
on  the  under  side,  to  characteristic  bladder-like  struct- 
ures, every  sort  of  intermediate  form  exists,  and  as 
a  rule  these  produce  no  very  serious  results  on  the 
plant.  It  is  astonishing  how  great  a  number  of  such 
insects  a  plant  may  support  without  interfering  with 


THEIR  RELATION  TO  PLANTS  49 

its  power  to  maintain  life  and  reproduce  its  kind ;  which 
be  it  noted,  is  quite  a  different  matter  from  an  injury 
which  will  make  the  plant  unprofitable  to  the  farmer 
or  fruit-grower. 

Scale  insects  are  close  allies  of  plant  lice  in  many 
ways  and  yet  totally  different  in  many  others.  The 
popular  name  is  derived  from  the  fact  that  most  of  the 
species  have  the  appearance  of  a  fragment  or  scale  of 
tissue  plastered  upon  or  against  the  bark  or  foliage 
of  the  plant  attacked.  And  so  we  have  soft  scales  and 
armored  scales,  which  differ  radically  from  each  other. 
In  the  soft  scales,  so  named  because  the  outer  covering 
is  usually  waxy  in  texture,  the  outer  covering  or  scale 
is  part  of  the  insect  itself,  not  separable  from  it  in  any 
way,  and  the  term,  scale  insect,  is  strictly  correct.  In 
the  armored  scales,  on  the  other  hand,  the  scale  or 
covering  mass  is  tougher,  more  parchment-like,  and 
forms  no  part  of  the  insect,  although  produced  or  ex- 
creted by  it.  It  is  possible,  therefore,  to  lift  the  scale 
without  in  any  way  interfering  with  the  creature  be- 
neath it;  the  covering  being  formed  in  part  by  the 
cast  skin  of  the  insect  and  in  part  by  a  fibrous  excre- 
tion from  special  glands. 

Scale  insects,  like  plant  lice,  are  capable  of  enormous 
feats  in  the  reproductive  line,  one  thousand  million  de- 
scendants for  a  single  pair,  during  a  single  season, 
having  been  figured  out  for  one  of  the  species!  Thus, 
given  a  scale  introduced  without  natural  checks  into 
a  region  where  conditions  favor  it,  and  the  effect  upon 
its  host-plant  can  be  readily  imagined.  The  practical 
experience  of  the  Pacific  Coast  with  the  cottony  cushion 
scale  on  citrus  fruits,  and  of  the  Atlantic  Coast  with 
the  San  Jose  scale,  are  recent  instances  that  illustrate 
the  destructive  powers  of  scales;  the  first  a  soft,  the 
latter  an  armored  form. 

4 


So  INSECTS 

Scale  insects  feed  on  the  juices  of  their  host  as  do 
the  plant  lice,  differing  in  the  fact  that  they  are  more 
or  less  fixed  to  a  single  spot  on  the  plant:  absolutely 
fixed  in  the  armored  scales,  with  a  very  limited  range 
of  motion  during  a  part  of  their  life  in  the  soft  scales; 
the  latter  being  in  some  cases  not  far  removed  from  the 
mealy  bugs  which  are  active  throughout  their  life  and 
produce  a  powdery  material  that  does  not  form  a  com- 
plete covering.  Some  produce  living  young  and  breed 
throughout  the  season,  like  the  San  Jose  scale;  others 
are  oviparous  and  have  only  one  distinct  brood,  like  the 
cottony  maple  scale.  In  some  there  are  only  a  few 
eggs,  in  others  they  are  almost  uncountable,  and  thus 
there  is  a  great  range  in  the  life  cycle,  although  the 
nature  of  the  injury  done  is  always  the  same. 

One  characteristic  feature  is  the  difference  between 
the  sexes.  The  males,  throughout  the  Coccidce,  are 
very  minute,  frail,  two- winged  creatures  without  func- 
tional mouth  parts  and  two  pairs  of  eyes;  one  pair 
replacing  the  lost  feeding  organs.  These  males  are 
often  furnished  with  long  anal  styles  or  filaments,  and 
their  only  function  is  to  fecundate  the  female.  The 
latter  feeds  throughout  life,  never  becomes  winged,  and 
her  dead  body  often  serves  as  a  cover  or  shelter  for  the 
egg  mass  that  she  produces. 

The  injury  caused  is  primarily  due  to  the  abstrac- 
tion of  sap;  but  quite  a  number  of  species  produce  a 
distinct  poisoning  of  the  bast  or  bark  tissue,  often 
evidenced  by  a  red  or  purplish  discoloration.  Where 
this  occurs  the  twig  or  branch  dies  sooner  or  later. 
Sometimes  pits  or  depressions  are  formed  where  a 
little  group  of  scales  is  lodged  and,  in  fact,  there  are 
infinite  variations  in  the  character  of  the  injury,  due 
to  the  peculiarities  of  the  plant  attacked  and  to  the 
method  of  feeding  by  the  insects.  Some  of  the  soft 


THEIR  RELATION  TO  PLANTS 


FIG.  15. — Development  of  the  San  Jose"  scale:  a,  larva;  6,  its  antenna;  c, 
female  with  young  showing  through  body  wall;  d,  outline  of  anal  plate;  e,  male 
adult. 


52  INSECTS 

scales  produce  honey-dew  in  great  quantity,  and  the 
resulting  soot  fungus  does  almost  as  much  injury  as 
the  insect.  In  the  olive  and  citrus  groves  of  the  Pacific 
Coast,  trees  infested  by  the  black  scale  are  often  recog- 
nizable as  far  as  they  can  be  clearly  seen,  and  discolora- 
tion of  fruit  is  a  distinct  element  of  the  injury  caused. 

Quite  a  number  of  others  among  the  allies  of  scales 
and  plant  lice  produce  honey-dew  and  its  consequences, 
and  there  is  a  long  series  of  species,  including  the  leaf- 
hoppers,  tree-hoppers  and  others  of  the  Homopterous 
section,  that  cause  more  or  less  in  jury 'to  their  food 
plants  by  the  direct  robbery  of  the  vital  juice  or  sap; 
but  there  are  none  differing  so  greatly  from  the  methods 
of  plant  lice  and  scale  insects  as  to  require  special 
attention  here. 

A  somewhat  different  type  of  injury  is  caused  by 
some  tree-hoppers  and  Cicadas  or  harvest  flies.  These 
do  little  or  no  harm  by  direct  feeding;  but  utilize  the 
twigs  and  branches  of  the  plants  on  which  they  live 
as  places  of  deposit  for  their  eggs  in  such  a  way  as  to 
kill  or  severely  cripple  them.  Some  of  the  tree-hoppers 
cut  little  slits  in  the  twigs  to  receive  their  eggs,  and 
these  slits  never  heal.  The  tendency  is  rather  to  an 
enlargement  of  the  scar  which  permanently  weakens  the 
shoot  and  sooner  or  later  causes  a  break.  The  chief 
sinner  in  this  direction  is  the  periodical  Cicada,  better 
known  as  the  "ly-year  locust,"  and  wherever  and 
whenever  that  makes  its  appearance  in  numbers,  the 
tips  of  the  forest  trees  in  early  fall  show  brown  ends 
as  if  a  fire  had  passed  over  them.  In  such  forests  it 
means  only  a  moderate  pruning  and  no  real  injury  to 
the  trees;  but  in  orchards,  especially  of  young  trees, 
injury  is  often  severe,  weakening  the  shoots  and  branches 
so  that  they  break  under  a  load  of  fruit.  And  these 
punctures  also  refuse  to  heal,  and  remain  permanent 


THEIR  RELATION  TO  PLANTS 


S3 


sources  of  weakness,  apt  to  result  in  a  break  at  any 
time.  I  would  never  advise  planting  a  nursery  tree 
whose  trunk  had  been  used  by  Cicadas  for  ovipositing. 
In  the  Heteropterous  series  the  species  are  usually 
larger;  but  the  life  histories  are  simpler  and  the  injury 
is  not  materially  different.  Here,  among  the  plant 


FIG.   16. — a,  Ceresa  bubalus,  a  tree-hopper,  ovipositing  in  slits  b;    the  eggs,  d, 
arranged  as  at  c;   old  scarred  punctures  at  e. 


bugs,  the  poisoning  effect  already  referred  to  is  often 
noticeable,  and  is  frequently  of  more  importance  than 
the  exhaustion  caused  by  the  direct  feeding.  The 
chinch-bug  may  serve  as  the  best  known  example  of 
the  destruction  causable  by  these  species  and  of  the 
results  that  come  only  from  the  enormous  numbers 
in  which  they  feed.  There  is  nothing  here  but  a  direct 
loss  of  vitality  due  to  the  abstraction  of  the  plant  juices. 


54  INSECTS 

The  order  Orthoptera,  as  a  whole,  consists  of  plant 
feeders:  from  the  earwigs  to  the  crickets  there  are 
only  a  few  groups  where  vegetation  is  not  the  chief 
or  only  food.  The  earwigs  are  curious  because  of 
their  resemblance  to  beetles  and  their  large  anal  for- 
ceps, and  they  feed  largely  in,  though  not  always  on 
flowers.  Not  many  occur  in  North  America  and  their 
chief  interest  lies  in  the  fact  that  the  female  broods 
over  her  eggs  after  they  are  laid:  an  altogether  unusual 
character  in  this  series  of  species.  The  roaches  are 
not  normally  troublesome  to  growing  vegetation  and 
are  of  most  interest  as  household  pests,  where  more 
is  said  of  them.  The  Mantidcz  or  graspers  is  the 
only  group  of  distinctively  predatory  species  in  the 
order  and  they  are  very  few  in  number.  The  Phasmidce 
or  "walking  sticks"  are  devourers  of  plant  tissue, 
interesting  because  of  their  resemblance  to  the  twigs 
and  leaves  among  which  they  live,  and  because  of 
their  habit  of  dropping  their  eggs  to  the  ground  with- 
out care  as  to  their  location  and  future ;  as  far  removed 
as  possible  from  the  habit  of  the  earwigs.  Their  injury 
to  the  plants  is  of  the  simplest  possible  description 
and  confined  to  a  partial  destruction  of  foliage,  which 
means  little  or  nothing  to  the  plant. 

The  grasshoppers,  on  the  other  hand,  are  among 
the  best  known  of  plant  destroyers.  Under  the  name 
"locusts"  their  ravages  have  been  written  of  in  the 
Bible  and  by  later  writers  on  conditions  in  Africa  and 
the  Mediterranean  countries.  The  migratory  locust 
has  thus  come  to  represent  the  very  type  of  destruc- 
tive invasion,  and  the  Rocky  Mountain  locust  or  grass- 
hopper in  our  own  country  is  not  less  well  and  unfavor- 
ably known  for  its  injuries.  ' 

The  short-horned  grasshoppers,  which  are  the 
species  now  under  consideration,  quite  usually  lay 


THEIR  RELATION  TO  PLANTS 

their  eggs  in  little  masses  in  holes  in  the  ground,  which 
they  bore  with  the  horny  valves  at  the  end  of  the 
body,  and  they  select  moderately  firm,  dry  ground  for 
that  purpose.  Much  moisture  is  dangerous  or  even 
fatal  to  the  eggs,  hence  it  is  in  desert  or  semi-arid 
countries  that  they  are  most  abundant.  Such  condi- 
tions in  our  country  exist  among  the  foot-hills  of  the 
Rocky  Mountains  and  no  place  that  I  have  ever  seen 
exceeds  that  region  in  the  variety  and  abundance  of 
its  grasshoppers  in  a  normal  season.  Sometimes, 
when  conditions  become  unusually  favorable,  grass- 


FIG.  17. — The  American  grasshopper  or  locust,  Schistocerca  americana. 

hoppers  may  become  so  very  abundant  that  the  vege- 
tation in  their  native  locality  is  insufficient  to  support 
them,  and  then  some  species  better  fitted  for  flight 
than  others,  take  wing  and  seek  new  feeding  grounds. 
Some  are  unable  to  get  very  far,  and  rest  as  close  to 
home  as  they  can,  starving  if  they  get  beyond  the  limits 
of  their  strength  without  discovering  new  pastures; 
but  other,  longer  winged  species,  accomplish  hundreds 
of  miles  from  the  Rocky  Mountains  to  the  Mississippi 
Valley,  alighting  first  where  cultivated  lands  begin. 
Thus  Kansas,  Nebraska  and  the  Dakotas  were  pre- 
eminently sufferers  from  grasshopper  invasions,  and 
not  infrequently  conditions  were  sufficiently  good 
there  to  permit  the  insects  to  lay  their  eggs,  providing 
for  a  brood  which  the  year  following  destroyed  the 


56  INSECTS 

vegetation  while  still  unfledged,  and  then  migrated 
yet  further  east  to  do  destructive  work  as  adults  and 
to  perish  gradually,  in  the  egg  stage,  in  the  moist  un- 
suitable soil.  No  one  who  has  not  seen  grasshoppers 
in  this  western  country  can  form  any  real  idea  of  their 
actual  abundance,  and  their  destructiveness  has  been 
the  theme  of  many  a  writer.  They  eat  any  green  thing 
if  they  must;  but  favor  the  low  plants  of  field  and 
meadow  so  long  as  they  last. 

Conditions  now  are  much  better  than  they  were 
and  can  never  again  be  quite  as  bad.  A  large  area  of 
what  was  at  one  time  ideal  breeding  ground,  is  now 
irrigated  and  under  cultivation,  and  the  enormous 
belt  of  alfalfa  and  other  crops  now  basing  the  foot- 
hills, checks  and  takes  up  the  migrating  hordes  that 
occasionally  start  from  the  uncultivated  areas.  The 
march  of  advancing  cultivation  spells  the  doom  of 
some  of  these  grasshopper  species,  as  it  has  that  of 
many  another  animal;  but  meanwhile  the  grass- 
hopper is  putting  up  a  good  fight  and  is  still  causing 
trouble. 

While  there  is  considerable  variation  in  grasshopper 
habits  and  life  history,  some  of  them  laying  their  eggs 
in  soft  or  decaying  wood  tissue,  there  is  little  in  the 
character  of  the  injury  caused;  it  is  always  a  direct 
eating  of  the  plant,  rarely  threatening  its  life,  however 
much  it  may  be  injured  for  agricultural  purposes. 

The  long-horned  or  meadow  grasshoppers  are  most 
abundant  in  the  places  shunned  by  the  short-horned 
species.  They  delight  in  moist  meadows,  in  reedy 
open  swamps,  and  are  abundant  in  the  marshes  along 
the  sea  and  lake  coasts.  They  are  usually  of  some  shade 
of  green  in  color,  and  have  a  more  or  less  well  marked 
blade-like  ovipositor,  by  means  of  which  they  lay  their 
eggs  in  the  stems  or  leaves  of  the  grasses  and  other 


THEIR  RELATION  TO  PLANTS  57 

vegetation  among  which  they  live.  They  are  largely 
seed  feeders  when  seeds  are  to  be  obtained,  but  eat 
grassy  tissue  as  well.  A  character  of  interest  is  found 
at  the  base  of  the  wings  in  the  males,  where  the  over- 
lapping parts  are  ridged  and  toughened  to  form  a 
stridulating  or  musical  apparatus  of  a  very  effective 
order.  The  best  known  among  this  type  are  the  Katy- 
dids, which  are  often  tree  and  shrub  dwellers  but  do 
not  differ  markedly  in  other  respects  from  the  more 
lowlv  meadow  inhabitants. 


FIG.  1 8. — A  long- horned  grasshopper,  Microcentrum  sp. 

The  crickets  are  very  diverse  in  their  habits,  both 
as  to  dwelling  places  and  as  to  food;  some  confined  to 
vegetable  matter  only,  a  few  omnivorous  and  the  tree 
crickets  carnivorous.  The  latter  are  really  the  only 
injurious  forms  for,  while  they  eat  plant  lice  and  similar 
creatures,  they  lay  their  eggs  in  the  shoots  of  plants 
and  sometimes  cause  their  death;  but  this  is  an  in- 
significant item  as  against  their  usefulness  from  the 
farmer's  point  of  view. 

On  the  whole,  while  the  order  Orthoptera  contains 
many  plant  destroyers,  the  destruction  is  rarely  total: 
that  is,  it  is  confined  to  defoliation  which  does  not 
threaten  the  actual  life  of  the  plant,  however  completely 
it  may  destroy  its  value  agriculturally. 


5$  INSECTS 

In  the  order  Coleoptera  or  beetles  we  have  a  very 
large  number  of  species  and  a  very  great  diversity  of 
habits.  They  live  under  almost  every  conceivable 
condition  where  insect  life  is  possible  at  all,  and  there 
is  no  organic  matter,  living  or  dead,  which  is  not  eaten 
by  some  Coleopteron  in  either  the  adult  or  larval  stage. 
We  may  therefore  expect  to  and  do  find  enemies  to  all 
sorts  of  plant  life  and  there  is  no  part,  from  the  tip  of 
the  finest  rootlet  to  the  topmost  leaf,  that  is  exempt. 

Just  how  it  happened  that  certain  types  of  struct- 
ure became  associated  with  certain  feeding  habits 
makes  a  very  interesting  question  on  which  there  are 
widely  divergent  opinions;  but  for  our  purpose  we  can 
simply  accept  the  fact  that  the  general  life  habits  of 
any  beetle  can  be  approximately  stated  from  an  ex- 
amination of  the  feet,  the  antennae  or  feelers  and  the 
general  type  of  mouth.  There  are  exceptions  in  every 
large  group  as  the  result  of  special  adaptation,  but  for 
general  purposes  the  test  answers  well. 

We  have  a  large  series  of  species,  most  of  them 
terrestrial  but  a  few  aquatic,  in  which  the  antennae 
are  slender,  made  up  of  usually  eleven  joints  of  similar 
form,  and  the  feet  are  5-jointed  on  all  legs.  All  these 
are  predatory  in  general  habits,  both  as  larvae  and 
adults,  and  none  are  characteristically  enemies  of  plant 
life.  There  are  some  that  eat  plants,  and  a  few  have 
caused  injury  at  times;  but  these  are  exceptional 
instances. 

Coming  next  in  the  order  of  series  are  the  Clavicorns 
in  which  the  antennae  are  thickened  toward  the  tip  so 
as  to  form  a  distinct  enlargement  or  club:  the  feet,  all 
of  them  with  the  same  number  of  joints,  though  the 
number  may  be  from  three  to  five,  none  of  them  with 
the  third  joint  lobed.  By  far  the  largest  part  of  this 
series  are  scavengers,  living  in  fermenting,  dry  or  de- 


THEIR  RELATION  TO  PLANTS 


59 


caying  animal  and  vegetable  material  of  all  kinds. 
A  very  few,  comparatively,  are  predatory  and  yet  a 
smaller  number  are  feeders  upon  living  vegetation; 
none  of  them  in  any  very  characteristic  way  nor  so  as 
to  threaten  the  existence  of  the  plant  attacked;  but 
still  giving  variety  to  the  series. 

These  are  followed  by  the  Serricornia,  in  which  the 
antennae   have   the    joints    more    or    less   trigonate,    or 


FIG.  19. — Antennal  structure  of  Coleoptera.  a,  filiform;  b,  clavate;  c,  serrate; 
d,  lamellate;    e,  moniliform. 


saw-toothed,  and  the  feet  5-jointed  as  a  rule;  always 
with  the  same  number  on  all  feet.  Among  these  the 
vast  majority  are  vegetable  feeders,  but  this  vegeta- 
tion may  be  dead  or  alive,  and  most  of  the  feeding  is 
on  woody  tissue  rather  than  foliage.  The  "  click  beetles, ' ' 
"snapping  beetles"  or  Elateridce  are  characteristic 
members  of  this  series,  and  as  wire- worms  their  larvae 
are  very  often  feeders  on  root  tissue.  The  beetles  gain 
their  common  names  by  the  loose-jointed  structure 


6o 


INSECTS 


between  the  prothorax  and  the  rest  of  the  body,  and 
their  habit  of  snapping  or  springing  up  with  a  jerk 
when  turned  on  their  backs.  The  wire-worms  gain 
their  name  from  the  tough  leathery  texture  combined 
with  a  slender  wormlike  form  and  most  of  them  feed 
underground,  devouring  the  roots  of  many  sorts  of 
plants,  severely  injuring  or  actually  destroying  such 
as  they  attack.  But  there  is  also  a  large  contingent 
that  lives  in  woody  tissue — nearly  always  dead  tissue 
and  quite  generally  such  as  is  well  advanced  in  decay. 
Thu  insects  can  scarcely  be 
called  borers,  because  they  are 
hardly  fitted  to  make  their  way 
in  sound  wood ;  but  in  logs  and 
stumps  or  even  dead  standing 
trunks  they  are  often  found  in 
goodly  numbers. 

Typical  wood-borers  are 
found  among  the  Buprestidce, 
which  are  usually  metallic,  hard- 
shelled  beetles,  generally  of  good 

size,  often  with  handsomely  sculptured  wing-covers.  In 
the  larval  stage  these  are  known  as  flat-headed  borers 
or  "hammer-heads"  because,  immediately  behind  the 
mouth  structures  the  first  thoracic  segment  is  much  en- 
larged and  often  chitinized,  giving  the  appearance  of  a 
very  broad,  flattened  head,  followed  by  a  long  slender 
body  in  which  all  the  joints  are  well  marked.  These  bor- 
ers work  in  the  bast  and  sap-wood  of  the  trunks  and 
branches  of  trees  and  shrubs,  making  shallow  galleries  of 
more  or  less  characteristic  shape  and  sometimes  enor- 
mous length.  A  single  borer  not  over  an  inch  and  a 
quarter  long,  may  make  a  gallery  an  eighth  of  an  inch 
wide  and  over  ten  feet  in  length,  leaving  a  trail  of  dead 
tissue  that  the  tree  in  many  cases  cannot  replace  or  mend. 


FIG.  20.— Click-beetle  and  wire- 
worm  from  side  and  top. 


THEIR  RELATION  TO  PLANTS 


61 


If  this  trail  is  along  or  with  the  grain,  not  much  harm  is 
done;  but  in  many  cases  it  tends  to  a  girdling  or  to  a 
cutting  across  the  grain  that  involves  a  large  part  of  the 
circumference.  And  when  there  are  several  such  borers 
at  work  in  one  tree,  fatal  results  follow.  I  have  seen 
entire  orchards  of  pear  trees  and  fields  of  blackberry 
killed  by  borers  of  this  character. 

Sometimes,    the    larva,    instead   of   making    a   long 
narrow  gallery,  eats  out  an  irregular  chamber  beneath 


FIG.  21. — Flat-head  apple  borer:  a, 
larva;  b,  pupa;  d,  adult. 


FIG.  22. — An  irregular  gallery  made 
by  a  flat-head  borer. 


the  bark,  and  that  sort  of  injury  is  not  nearly  so  serious, 
since  it  does  not  so  much  interrupt  the  circulation  of 
sap.  So  there  is  quite  a  little  difference  of  habit  in  the 
selection  of  the  tree  to  be  attacked.  Some  species 
never  enter  living  trees  and  these  are,  perhaps,  in  the 
majority;  but  some  never  attack  other  than  healthy 
tissue.  As  a  rule,  if  trees  are  found  infested  by  flat- 
headed  borers,  it  can  be  assumed  that  they  were  al- 
ready in  rather  poor  condition  before  the  entry;  this 
new  attack  marking  the  first  step  in  nature's  attempt 
to  get  rid  of  an  organism  no  longer  aggressively  healthy. 


62 


INSECTS 


In  those  species  that  attack  dead  tissue  only,  some 
of  which,  like  the  cigarette  beetle  and  death  watch, 
are  treated  in  Chapter  X,  we  get  an  approach  to  the 
scavenger  type;  and  yet  the  term  scavenger  seems 
scarcely  a  fitting  one  since  the  material  attacked  is 
not  in  a  condition  of  either  ferment  or  active  decay. 

In  the  "soldier  beetles"  and  "fireflies,"  which  by 
the  form  of  their  antennae  are  members  of  this  series, 


FIG.  23. — May  beetle:    i,  pupa  in  earthen  cell;   2,  larva  or  white  grub; 
3,  4,  beetle  from  side  and  above. 


we  have  a  wide  departure  from  the  general  feeding 
habit,  most  of  them  being  predatory  in  the  larval 
stage,  and  feeders  among  flowers,  where  they  feed  at 
all,  as  adults. 

The  series  Lamellicornia,  containing  species  with 
the  feet  5 -jointed  and  the  antennae  terminated  by  a 
leaf -like  club,  includes  vegetable  feeders  almost  ex- 
clusively, in  both  larval  and  adult  stages,  and,  in  gen- 
eral, the  feeding  is  upon  live  vegetation.  There  are 


THEIR  RELATION  TO  PLANTS 


the  usual  exceptions  of  course,  but  really  very  few  in 
number.  The  common  "May-beetle"  or  "June-bug" 
may  be  selected  as  a  good  type  and  this,  as  an  adult, 
exemplifies  the  habits  of  the  series  in  its  voracious 
feeding.  Most  of  the  beetles  of  this  series  feed  in  the 
adult  stage,  and  in  almost  all  instances  it  is  a  direct 
straightforward  devouring  of  growing  tissue  which 
does  not  endanger  the  life  of  the  plant.  In  the  larval 
stage  the  species  are  known 
as  white-grubs  and  in  this  they 
are  much  more  dangerous  since 
they  feed  upon  the  roots,  often 
destroying  the  smaller  plants 
such  as  grasses,  berries  and  the 
like.  The  step  from  living  to 
dead  vegetable  matter  is  a  very 
short  one  and  so  we  find  here 
also  quite  a  number  of  feeders 
on  dead  or  even  decaying 
plants,  which  of  course  are  not 
among  the  direct  plant  enemies. 
In  that  great  series  of  Phy- 
tophaga,  which  contains  the 
families  Chrysomelidce  or  plant 

beetles,  and  Ceramby  tides  or  long-horned  beetles,  we  find 
all  the  tarsi  or  feet  apparently  4-jointed,  the  third  joint 
lobed  or  divided  into  distinct  parts.  This  is  a  very  char- 
acteristic structure  and  almost  always  indicates  a  leaf- 
feeder.  Most  of  the  adult  beetles  in  the  Chrysomelidae 
feed  very  simply  and  openly  on  leaf  tissue,  devouring 
without  plan  or  aim  except  to  get  enough.  Occasionally 
we  do  get  some  characteristic  bit  of  feeding  like  that 
of  some  flea  beetles  which  eat  little  round  holes,  or 
make  channels  that  render  their  work  readily  identi- 
fiable. The  larvae  vary  more  in  their  habits  and,  while 


FIG.  24. — Tarsi  of  Coleoptera: 
a,  normally  5  -  jointed  ;  b,  4- 
jointed ;  c,  4-jointed  with  srd  joint 
lobed;  d,  same  from  side:  c  &  d 
always  indicate  a  plant-feeder. 


64  INSECTS 

the  vast  majority  are  soft,  naked,  slug-like  creatures, 
similar  to  those  of  the  potato  beetle,  or  only  scantily 
clothed  like  those  of  the  elm  leaf  beetle,  there  are  some 
that  are  more  slender,  white,  and  worm-like,  mining 
in  stems,  leaves  or  even  roots,  and  making  more  or 
less  characteristic  galleries,  channels  or  chambers. 
They  may  be  only  surface  channels  like  those  made 
on  cucurbs  by  certain  species  of  Diabrotica;  they  may 
be  real  borings  like  those  made  in  root  tissue  by  some 
flea  beetles;  or  they  may  be  mines  in  leaf  tissue,  like 
those  made  by  some  of  the  species  of  Hispids.  It  is 
rare  that  the  attack  of  a  Chrysomelid  really  threatens 
the  life  of  a  plant,  though  there  are  exceptions  to  this; 
the  grape-vine  root- worm  for  instance,  and  other 
root-feeders. 

In  the  long-horned  beetles,  or  CerambycidcB,  the 
adults  do  very  little  feeding;  but  the  larvae  are  borers 
in  woody  tissue  or  in  stems  of  plants,  differing  from 
those  of  the  Buprestids  by  being  more  cylindrical 
and  with  a  less  prominently  dilated  anterior  portion. 
They  are  known  as  round-headed  borers  as  distin- 
guished from  the  flat-headed  kind  already  described, 
and  their  galleries  in  section  are  nearly  round  instead 
of  transversely  oval.  As  a  rule,  also,  they  are  more  gen- 
erally borers  in  heart-wood  and  do  not  make  the  irreg- 
ular shallow  galleries  under  bark  that  are  so  char- 
acteristic of  the  flat-headed  types.  There  is  no  part 
of  a  tree  that  is  exempt  from  their  attacks:  from  the 
roots  to  the  very  tips  of  the  twigs  it  may  be  in- 
fested, and  they  do  not  confine  themselves  to  sick  or 
dying  trees  either:  a  perfectly  sound  tree  is  just  as 
likely  to  be  attacked  as  any  other  and,  indeed,  some 
species  are  found  in  sound  trees  only.  There  are  many 
interesting  points  connected  with  the  development 
of  these  borers,  the  life  period  of  some  of  them  being 


THEIR  RELATION  TO  PLANTS  65 

drawn  out  enormously  under  unfavorable  conditions. 
Thus,  if  a  piece  of  infested  timber  is  worked  up  into 
furniture,  a  larva  which  normally  matures  in  two  or 
three  years  may  live  for  eight  or  ten  years  or  even 
longer;  and  in  some  cases  wainscoting  has  been  found 
infested,  several  years  after  it  has  been  in  place,  var- 
nished and  polished  so  as  to  forbid  the  idea  that  some 
misguided  adult  oviposited  there  after  the  boards 


FIG.  25. — Round- head   apple   borer:   a,  puncture  where  egg  is  laid;    6,  same 
in  section;  e,  hole  from  which  beetle  has  issued;  /,  same  in  section;  g,  pupa. 

were  in  position.  Some  species  require  the  wood  in 
a  particular  condition  to  secure  their  best  development, 
and  so  a  beetle,  before  laying  its  egg,  may  girdle  the 
twig  so  as  to  interrupt  the  flow  of  sap  and  then  oviposit 
above  the  girdled  point.  Other  larvae  bore  into  live 
twigs  and,  when  ready  to  transform  to  the  pupal  stage, 
cut  through  from  the  inside  until  only  the  bark  and  a 
mere  shred  of  woody  tissue  remain.  Then  the  burrow 
is  securely  plugged  with  sawdust  and  the  larva  retreats 
5 


66  INSECTS 

into  its  gallery,  above  the  point  of  cincture,  certain 
that  the  next  high  wind  will  bring  it  safely  to  the  ground. 
Considering  the  enormous  variety  of  species  and  the 
number  of  points  attacked,  it  is  surprising  that  the 
amount  of  injury  caused  is  not  much  greater  than  it 
is.  But,  aside  from  the  natural  checks,  the  insects 
grow  slowly  in  the  larval  stage  and  are  rarely  great 
eaters;  the  borings  of  some  of  them  being  surprisingly 
short,  considering  the  size  of  the  larva  and  the  length 
of  time  it  feeds;  furthermore,  the  twig  and  branch 
borers  in  most  cases  produce  only  a  more  or  less  in- 
judicious pruning,  while  the 
•  borings  in  the  heart  wood 
on  a  large  tree  do  not  neces- 
sarily threaten,  its  existence. 
Still,  these  round-headed 
borers  may  be  accounted 
among  the  more  serious 
enemies  of  woody  plants. 

FIG.   26.—  Bean- weevil,    natural  A  little  offshoot  from  the 

size  and  enlarged,  and  a  much  in-  ,        ,    r       . .         ,  , 

fested  bean.  plant-feeding  beetles  are  the 

BruchidcB,  commonly  known 

as  bean-  and  pea-weevils  because  the  majority  of  them 
attack  the  seeds  of  plants  belonging  to  the  Leguminoscz 
or  pod-bearing  family.  This  includes  not  only  the  bean 
and  pea  of  the  garden,  but  such  tree  forms  as  the  locusts, 
and  almost  every  series  has  its  own  species  of  Bruchid 
that  lives  and  comes  to  maturity  in  the  seeds.  The  term 
weevil  is  not  strictly  applicable  to  these  insects  for,  al- 
though the  head  is  very  small  and  pointed,  it  is  not  pro- 
duced into  a  snout,  and  the  body  is  unusually  obese,  the 
wing-covers  squarely  cut  off  behind  and  leaving  a  large 
area  of  abdomen  exposed  posteriorly. 

Next  comes  a  series  known  as  the  Heteromera,  in 
which  the   anterior  and  middle  feet  have   five  joints 


THEIR  RELATION  TO  PLANTS  67 

but  the  posterior  four  joints  only.  It  includes  a  great 
variety  of  species,  many  of  them  of  sombre,  uniform 
color,  shunning  the  light,  living  in  concealment  and 
often  or  even  generally  feeding  on  dead  or  dry  vege- 
table matter.  Yet  there  are  exceptions  to  this,  as  for 
instance  the  blister  beetles  which,  in  the  larval  stage, 
are  semiparasitic,  and  as  adults  feed  ravenously  on 
vegetation.  When  they  are  feeders  on  living  plants, 
however,  it  is  as  straight-forward  devourers  of  leaf 
tissue  that  they  appear,  and  they  do  not  threaten  the 
existence  of  the  plant  attacked,  however  much  they 
may  injure  it  for  the  farmer's  purpose. 

And  now  we  get  the  Rhynchophora  or  snout  beetles 
which,  broadly  speaking,  include  the  bark  beetles  or 
Scolytids  and  with  them  some  of  the  most  dangerous 
enemies  to  plant  life.  Popularly  most  of  these  species 
are  known  as  weevils  and,  so  far  as  I  am  aware,  all  of 
them  are  plant  feeders.  And  there  is  no  part  of  the 
plant  from  root  to  tip  that  is  not  attacked;  no 
stage  from  seed  to  pollen  that  is  not  eaten  by  them. 
They  are  among  the  oldest  of  the  Coleoptera  in  the 
geologic  record  and  have  adapted  themselves  to  life 
on  vegetation  under  all  sorts  of  conditions.  The  term 
snout  beetles  calls  attention  to  one  of  the  most  prom- 
inent external  structures — the  elongated  head  drawn 
out  into  a  beak  of  varying  length,  at  the  end  of  which 
the  small  mouth  parts  are  situated.  For  feeding  pur- 
poses these  do  not  seem  to  be  especially  well  designed, 
indeed  in  many  species  the  mandibles  are  deciduous 
and  are  shed  soon  after  the  adult  is  developed;  but 
for  hiding  and  placing  the  eggs  no  better  nor  more 
practical  tool  can  be  imagined.  For  instance,  almost 
every  one  that  has  gathered  nuts  has  had  the  experi- 
ence of  finding  some  of  them  wormy,  with  absolutely 
no  trace  of  an  opening  on  the  outside  to  show  how 


68 


INSECTS 


that  worm  or  grub  ever  got  into  it.  If  the  grub  is  bred 
to  maturity  it  will  develop  into  a  snout  beetle  with  a 
very  slender  brown  beak,  from  one  half  to  three  quarters 
of  an  inch  in  length  or  even  longer.  With  this  long 
snout  the  parent  punctures  the  forming  burr  of  the 
chestnut  or  husk  of  the  other  nuts,  and  into  the  very 
centre  it  runs  its  minute  channel.  It  then  turns,  places 
an  egg  into  the  mouth  of  the  opening  so  made  and 
again  turning,  slowly  and  gradually  forces  the  egg  into 
place  with  the  beak.  The  rapidly  growing  plant  tissue 
effaces  all  trace  of  this  puncture,  and  there  we  have 


FIG.  27. — A  nut- weevil:   Balaninus  sp.:   a,  from  above;   b,  from  side;  c,  larva. 

our  embyro  grub  already  in  place,  almost  before  there 
is  any  differentiation  between  shell  and  kernel.  It  is 
interesting  to  note  in  this  connection  how  carefully 
nature  guards  against  the  extinction  of  any  of  her 
creatures  by  a  season  of  adverse  conditions.  A  species 
dependent  upon  the  hickory-nut  for  instance  might, 
in  case  of  a  total  failure  of  that  crop  for  some  one  year, 
become  locally  exterminated  if  all  specimens  followed 
the  same  routine.  But  were  we  to  put  100  grubs  into 
confinement  in  fall,  when  nuts  are  ripe,  and  permit 
them  to  go  underground  to  pupate,  we  would  probably 
get  not  over  sixty  adults  the  spring  following;  and  if 


THEIR  RELATION  TO  PLANTS  69 

we  left  our  specimens  undisturbed  we  would  probably 
get  thirty  more  the  next  year  thereafter  and  the  re- 
mainder the  third  year  following.  This  seems  to  be 
rather  a  wide-spread  provision  for  tiding  insects  over 
a  bad  season  and,  not  only  in  the  snout  beetles  but  in 
many  other  groups,  single-brooded  species  that  pass 
the  winter  in  the  pupal  stage,  may  lie  over  for  one 
or  even  two  years  after  the  bulk  of  the  brood  has 
become  adult. 

By  virtue  of  this  provision  for  placing  eggs,  many 
of  the  snout-beetle  larvae  are  feeders  in  blossoms,  fruits 
and  seeds,  and  enormous  damage  is  caused  to  trees 
and  plants  by  limiting  their  seed  bearing  powers.  When 
these  fruits  are  of  commercial  importance  like  the  plum, 
the  horticulturist  classes  the  "plum  curculio"  as  a 
first  class  pest  and  a  subject  for  investigation  by  the 
economic  entomologist.  If  I  mention  once  again  the 
cotton -boll  weevil,  and  cite  as  a  further  example  of  seed 
destruction  the  strawberry  weevil,  the  danger  of  this 
sort  of  insect  to  plant  life  may  be  appreciated.  It  is 
of  course  the  larva  that  does  the  injury,  and  curculio 
larvae  are  all  more  or  less  grub-like  in  character;  mostly 
white  like  the  generality  of  internal  feeders,  and  usually 
with  a  brown  chitinous  head  furnished  with  well-de- 
veloped jaws  or  manidbles. 

Blossoms,  fruits  and  seeds  furnish  only  one  article 
of  diet  for  weevils  and  their  larvae:  many  bore  into 
the  stems  of  herbaceous  plants,  as  the  rhubarb  weevil; 
others  bore  into  wood  tissue  like  the  white  pine  weevil, 
and  the  latter,  by  killing  off  the  leading  shoots,  fre- 
quently distorts  a  tree  to  such  an  extent  as  to  make 
it  commercially  useless.  A  comparatively  small  number 
are  external  feeders  on  plant  tissue  like  the  clover- 
leaf  beetle;  a  few  make  tubes  or  other  cases  out  of  the 
leaves  on  which  they  feed,  and  some  cause  galls  or 


70  INSECTS 

other  enlargements.  There  is,  therefore,  scarcely  a 
method  of  attack  that  is  not  represented  among  the 
snout  beetles. 


FIG.  28. — A  piece  of  hickory  bark,  illustrating  the  work  of  Scolytus 
4-spinosus  and  its  larva. 

The  Scolytids  or  bark  beetles  deserve  separate 
mention,  as  they  are  among  the  most  dangerous  of  all 
tree  enemies  and  the  greatest  destroyers  of  wood  tissue, 


THEIR  RELATION  TO  PLANTS  71 

living  or  dead.  The  name  bark  beetle  is  a  misnomer 
for  many  of  the  species,  which  never  bore  into  or 
under  bark  at  all;  but  it  applies  well  to  a  very  large 
number  that  make  characteristic  borings  or  galleries 
beneath  the  bark  or  in  the  sap-wood.  In  forms  of 
which  the  common  fruit  bark  beetle  may  be  considered 
typical,  the  adult  bores  a  longitudinal  channel  in  the 
sap-wood  and  lays  eggs  on  each  side  in  little  notches 
cut  for  that  purpose.  These  beetles  are  all  more  or 
less  cylindrical,  slender  and  elongate,  with  a  very  short 
or  scarcely  perceptible  snout  and  well-developed  jaws 
or  mandibles.  The  larvae  that  hatch  from  the  large 
white  eggs  are  of  the  usual  grub-shape,  white  with 
brownish  head,  and  each  larva  makes  its  burrow  at 
right  angles  to  the  main  gallery,  diverging  a  little  up- 
ward or  downward  as  it  increases  in  size  so  as  to  avoid 
its  neighbors,  and  making  a  pattern  so  distinctive 
that  the  species  may  be  recognized  by  its  borings  alone. 
Quite  usually  beetles  of  this  character  attack  trees  that 
are  a  little  weakened  or  unhealthy,  but  some  take  to 
perfectly  sound  trees  and  cause  serious  trouble.  Other 
species  bore  into  the  heart  wood,  their  galleries  being 
cylindrical,  often  blackened  or  discolored,  and  these 
are  sometimes  called  shot-hole  borers. 

No  kind  of  tree  is  exempt  from  the  attacks  of 
such  beetles,  and  thousands  of  acres  of  forest  lands 
in  all  sections  of  the  United  States  are  annually  de- 
stroyed by  them.  And  much  timber  is  rendered  useless 
or  lessened  in  value  by  the  borings  which  disfigure  or 
weaken  it,  where  the  life  of  the  tree  itself  is  not  threat- 
ened. In  trunk,  in  twig  and  even  in  the  roots  these 
Scolytid  borers  are  found,  and  our  knowledge  of  them 
still  leaves  much  to  be  desired.  Only  a  small  propor- 
tion of  our  species  are  actually  known,  and  their  classi- 
fication at  present  is  merely  tentative.  They  are  re- 


72  INSECTS 

ceiving  more  attention  now  than  ever  before,  and  they 
merit  more  attention  than  they  are  receiving. 

Altogether,  the  Coleoptera,  among  the  dominant 
orders,  furnish  a  very  large  number  of  destroyers  of 
plant  tissue  living  and  dead,  and  many  that  may  be 
ranked  as  destroyers  of  plant  life. 

The  order  Lepidoptera  includes  the  butterflies  and 
moths  and  their  larvae  are  known  as  caterpillars.  Cater- 
pillars with  few  exceptions  feed  on  plant  tissue,  hence, 
as  a  whole,  the  members  of  the  order  may  be  consid- 
ered as  enemies  of  plant  life.  Mainly  they  are  open 
and  above-board  enemies:  direct  feeders  upon  the  leaf 
tissue,  without  modification  or  concealment.  Such 
feeding  in  itself  does  not  endanger  plant  life  except  in 
cases  where  there  is  an  unusual  number  of  caterpillars 
or  the  plant  is  one  that  will  not  survive  defoliation; 
therefore  the  number  of  species  dangerous  to  plant 
life  in  this  way,  is  not  really  very  great.  There  are 
such  species,  of  course,  for  in  the  State  of  Massachu- 
setts there  are  hundreds  of  conifers  dead  as  the  result 
of  defoliation  from  gypsy  moth,  and  in  general,  any 
species  that  can  completely  strip  a  tree  may  cause  its 
death. 

A  comparatively  small  number  of  Lepidopterous 
larvae  are  borers  in  woody  tissue,  and  these  are  mainly 
members  of  the  families  Sesiida,  Cossidce  and  Hepi- 
alidcB'.  all  Tineites  under  the  modern  classification. 
The  Sesiids  are  small  clear-winged  moths  resembling 
wasps  in  appearance,  and  their  larvae  bore  into  trees 
and  in  the  stems  of  herbaceous  plants.  The  peach 
tree  borers  are  types  of  the  former,  working  under  the 
bark  at  the  surface  of  the  ground  and  often  causing 
the  death  of  young  trees;  the  squash  borer  is  a  type 
of  the  latter,  boring  into  the  stem  of  the  plant  at  almost 
any  point;  but  most  often  at  the  base.  Both  types 


THEIR  RELATION  TO  PLANTS  73 

frequently  cause  the  death  of  the  plants  attacked; 
but  there  are  others,  like  those  attacking  the  trunks 
and  branches  of  oak  and  maple,  that  may  infest  their 
host  for  years  without  causing  obvious  harm.  Not 
only  the  tissue  above  ground  is  attacked,  for  one  species 


FIG.  29. — The  peach  borer,  Sanninoida  exitiosa;    male  above,  female  below. 

at  least  occurs  on  the  roots  of  grape,  and  others  are 
underground   on   oak. 

The  Cossids  are  much  larger  forms  and  correspond- 
ingly more  dangerous.  The  European  Zeuzera  pyrina 
or  wood-leopard  moth,  which  has  been  introduced 
into  the  eastern  United  States,  frequently  girdles 
young  trees  and  often  weakens  the  branches  of  older 
ones  to  such  an  extent  as  to  make  them  easy  victims 


74 


INSECTS 


to  wind  storms.  Some  of  our  own  carpenter  worms 
make  simpler  borings;  but  owing  to  their  methods 
of  work,  leave  sore  spots  that  often  form  points  of  en- 
trance for  germs  of  decay.  Thousands  of  oak  trees  in 
the  eastern  United  States  are  "doated"  as  the  result 


FIG.  30. — Wood-leopard  moth,  Zeuzera  pyrina:  a,  b,  larva;  c,  male;  d,  female 
moth;  e,  larva  burrow. 


of  the  work  of  these  borers;  stunted  in  growth  and 
useless  as  timber.  Fortunately  the  number  of  species 
is  small  and  very  few  of  them  are  at  all  numerous  in 
specimens. 

The  Hepialids  are  very  ancient  in  type  and  they 
are  few  in  number  of  species  and  specimens.  The 
larvae  are  large  and  make  large  channels  in  roots  and 


THEIR  RELATION  TO  PLANTS  75 

trunks;  but  I  have  never  known  of  any  serious  injury 
done  by  them. 

There  are  many  others  among  the  Tineid  families 
that  are  borers  in  herbaceous  and  shrubby  plants  and 
some  cause  galls  or  other  abnormal  swellings  in  the 
infested  stems;  and  there  are  many  others  that  mine 
or  bore  in  leaves,  causing  a  great  variety  of  disfiguring 
injury,  but  rarely  anything  that  threatens  the  life  of 
the  plant  itself.  Many  of  these  little  caterpillars  and 
a  few  larger  species  make  cases  or  covers  of  the  most 
diverse  character,  and  others  live  in  shelters  spun  by 
the  members  of  one  brood  from  a  single  laying  of  eggs. 
Some  live  altogether  in  silken  tubes  spun  by  the  cater- 
pillars, and  of  these  some  feed  underground  on  the 
roots  of  corn  and  other  plants.  Quite  a  number  feed 
inside  of  fruits,  like  the  Codling  moth  of  the  apple  or 
the  berry  moth  of  the  grape,  and  a  few  get  into  seeds 
like  the  Angoumois  grain  moth. 

We  have,  then,  among  the  Lepidoptera,  a  very  large 
number  of  feeders  on  vegetable  tissue,  that  destroy 
portions  of  the  plant  without  endangering  its  life, 
and  a  comparatively  few  that  are  really  dangerous  to 
the  existence  of  the  organism  attacked,  however  much 
it  may  be  injured  from  an  economic  standpoint. 

The  order  Hymenoptera  contains  a  large  number 
of  species  of  very  great  interest:  some  of  them  vitally 
important  to  the  continuation  of  plant  life,  and  on  the 
contrary  a  few  that  are  destructive  to  it:  but  it  is 
interesting  to  note  that  among  the  bees  which  have  been 
shown  in  the  preceding  chapter  to  be  among  the  great- 
est benefactors  of  plants,  we  should  also  find  an  element 
of  danger.  Plants  suffer  from  "blights,"  "rusts," 
"scabs"  and  a  variety  of  other  diseases  and,  recently, 
plant  pathologists  have  charged  that  bees  in  their 
visits  to  flowers  engaged  in  the  beneficial  work  of 


7  6  INSECTS 

pollination,  at  the  same  time  carried  also  the  germs 
of  fire-blight  and  similar  diseases,  introducing  them 
into  the  sensitive  tissues  of  the  blossom.  It  is  an  old 
story,  of  course,  that  disease  organisms  frequently  find 
entrance  through  wounds  made  by  insects;  but  that 
is  merely  putting  the  insects  on  a  par  with  other  causes 
that  produce  abrasions,  cuts  or  bruises:  this  is  a  dif- 
ferent matter,  the  insect  being  charged  as  the  active 
transmitter,  much  as  a  fly  carries  typhoid  germs  to  the 
human  organism. 

Direct  plant  feeders  are  found  among  the  Hymen- 
optera  in  the  Sessiliventres, — "saw-flies"  and  "horn- 
tails," — which  derive  their  technical  name  from  the 
fact  that  the  abdomen  is  joined  to  the  thorax  for  its 
full  width  and  is  thus  sessile,  while  in  the  majority  of 
the  species  in  this  order  it  is  stalked  or  pedunculate, 
attached  at  a  narrow  point  only.  The  saw-flies  are 
somewhat  clumsy  in  appearance  and  more  sluggish 
than  the  other  Hymenoptera,  the  body  rather  uniform 
in  size  from  end  to  end,  the  wings  large,  with  many 
complete  cells,  and  folded  over  the  back  when  at  rest. 
They  derive  their  common  name  from  the  fact  that  the 
ovipositor  is  made  up  of  parallel  blades  variously 
toothed  at  the  edge,  by  means  of  which  the  female 
cuts  a  slit  or  pocket  into  a  leaf,  stem  or  twig,  for  the 
reception  of  an  egg.  The  larvae  that  hatch  from  these 
eggs  are  caterpillar-like  in  appearance  but  have  five 
pairs  of  abdominal  prolegs  instead  of  four  or  less,  as 
is  the  case  in  the  true  caterpillars.  They  are  mostly 
feeders  on  foliage,  like  the  currant  worm,  and  they 
sometimes  appear  in  enormous  numbers ;  but  they  do  not 
often  threaten  the  life  of  the  plant.  Some  of  them  only 
scrape  the  surface  of  the  leaves  like  the  pear  slug, 
while  others  eat  characteristic  holes  in  them  like  the 
blackberry  saw-fly.  A  considerable  number  are  gall- 


THEIR  RELATION  TO  PLANTS  77 

makers,    largely    on    willow,    the    excrescences    being 
quite  characteristic. 

The  "horn-tails"  have  the  ovipositor  modified  into 
an  augur-like  process  for  making  holes  in  plant  tissue, 
and  the  larvae  are  mostly  borers:  some  in  wood,  most 


FIG.  31. — The  currant  worm:   a,  adults;    b,  larvae  in  various  stages  of  devel- 
opment; c,  pupa;  e,  eggs  along  veins  on  leaf. 


of  them  in  shrubs  or  grasses.  These  very  often  threaten 
the  life  of  the  plant  attacked,  especially  when  wheat  or 
other  grasses  are  infested.  But  on  the  whole  the  number 
of  these  boring  species  is  small,  nor  are  they  often 
numerous  in  examples. 

A  very  characteristic  set  of  species  is  found  in  the 
"gall- wasps"  or  Cynipids  now  ranked  as  a  superfamily 


78  INSECTS 

under  the  term  Cynipoidea.  These  gall-wasps  produce 
in  the  plants  attacked  abnormal  swellings  or  growths 
known  as  galls,  which  are  constant  for  every  species 
and  differ  as  the  species  differ.  Thus  for  those  forms 
whose  life  history  is  known,  the  gall  is  as  good  an  index 
to  its  kind  as  a  specimen  of  the  wasp.  And  the  re- 
markable point  is,  that  the  gall  is  purely  a  production 
of  the  plant  and  the  insect  has,  apparently,  nothing 
at  all  to  do  with  it.  The  female  lays  the  egg  arid  in 
due  time  a  minute  larva  hatches.  Immediately  there 
begins  to  develop  around  this  larva  an  abnormal  growth 
centered  by  a  smooth  cell  in  which  the  larva  lies,  a 
white  helpless  grub,  feeding  upon  the  exudations  that 
come  from  the  inner  side  of  the  cell.  The  relation  be- 
tween the  irritation  set  up  by  the  minute  larva  just 
out  of  the  egg  and  the  remarkably  complicated  struct- 
ure of  plant  cells  built  up  around  it  has  never  been 
clearly  elucidated  and  offers  an  excellent  opportunity 
for  research.  Some  galls  are  spongy  in  texture,  some 
are  solid;  some  are  filled  with  radiating  fibres  extend- 
ing from  the  central  cell  to  the  covering  sphere;  some 
are  no  larger  than  necessary  to  accommodate  the  insect 
and  yet  others  are  huge  bladder-like  affairs,  out  of  all 
proportion  to  the  size  of  the  larva.  Some  galls  are  on 
leaves,  some  on  twigs  and  branches  and  a  few  are  on 
roots.  On  the  roots  and  stems  the  growths  are  often 
corky  or  woody,  and  sometimes  mere  enlargements 
of  the  normal  growth.  More  generally  the  galls  are 
unicellular,  i.e.,  they  have  only  a  single  central  cell 
containing  one  larva;  but  very  often  also  they  are 
multicellular,  a  large  growth  containing  many  larval 
cells  which,  in  turn,  may  be  very  regularly  or  very 
irregularly  disposed  in  the  larger  mass. 

These  gall-wasps  have  a  number  of  very  interesting 
features.     Some  of  them  appear,  year  after  year,  males 


THEIR  RELATION  TO  PLANTS  79 

and  females,  without  variation;  always  making  the 
same  kind  of  gall.  Others  appear  in  spring  from  over- 
wintered galls,  normal  males  and  females:  the  latter 
lay  eggs,  galls  appear,  but  from  them  only  females 
make  their  appearance;  these  in  turn  lay  eggs  and  from 
their  galls  males  and  females  appear  again  the  year 
following.  This  is  termed  an  "alternation  of  genera- 
tions" and  so  long  as  the  galls  are  similar  and  the  fe- 


FIG.  32. — An  oak  gall,  made  by  Cynips  q-spongifica;   a,  showing  the 
larva  in  its  cell;  b,  exit  hole  of  adult. 

males  are  similar,  no  confusion  is  caused.  But  it  some- 
times happens  that  the  summer  generation  is  very 
different  in  appearance  from  the  hibernating  form, 
while  the  gall  itself  is  different  and  on  a  different  kind 
of  tree,  so  that  there  appears  to  be  no  sort  of  connec- 
tion between  them  until  the  life  history  has  been  com- 
pletely followed  out — no  light  task  in  species  of  this 
character.  For  some  species  no  males  have  ever  been 
found  and,  so  far  as  we  know,  these  are  maintained 
by  parthenogenetic  females  alone. 


8o  INSECTS 

It  also  happens  sometimes  that  a  normal  constituent 
of  plant  tissue,  like  tannin,  is  greatly  intensified  in  the 
gall  structure  which  may  contain  many  times  more 
tannic  acid  than  any  other  part  of  the  tree.  The  galls, 
therefore,  become  of  commercial  value  and  in  some 
localities  the  oak  forests  yield  a  considerable  revenue 
from  this  source. 

Few  Cynipid  galls  are  really  injurious  to  the  plants 
on  which  they  appear.  Those  on  the  leaves  are  never 
so;  those  on  twigs  are  rarely  so;  those  on  the  larger 
branches  sometimes  cause  a  choking  and  sometimes 
a  weakening  that  results  in  a  fracture  under  strain; 
but  frequently  a  badly  galled  branch  will  in  its  de- 
velopment split  off  and  shed  the  old  galls.  Root  galls 
sometimes  threaten  the  life  of  a  plant;  but  most  of 
the  fatal  galls  found  on  trees,  shrubs,  and  vines  are  due 
to  other  causes. 

In  the  Diptera  we  have  plant  feeders  in  great  variety , 
and  many  of  them  endanger  the  life  of  the  plants  at- 
tacked; but  they  have  a  decided  preference  for  soft 
tissues  and  there  are  no  borers  in  solid,  living  wood. 

Among  the  long-legged,  mosquito-like  species  with 
long  antennae,  the  crane-flies  have  larvae  that  live 
underground  and  feed  on  the  plant  roots.  They  are 
sometimes  called  "wire-worms"  because  of  their  long 
slender  form,  and  "leather-jackets"  because  of  their 
texture.  They  differ  from  the  beetle  larvae  that  are 
also  called  wire- worms,  by  the  more  cylindric  shape, 
the  more  pointed  head,  and  absence  of  legs.  Their 
feeding  on  roots  is  sometimes  extensive  enough  to 
cause  the  death  of  the  plant  attacked.  The  crane- 
flies  are  the  largest  of  the  long-legged  forms,  some  of 
them  measuring  with  legs  extended  nearly  three  inches. 

The  gall-midges  are  at  the  other  extreme  and  in- 
clude very  small  species  with  very  long,  often  prettily 


THEIR  RELATION  TO  PLANTS 


81 


beaded  antennae.  Their  larvae  are  little  footless  grubs, 
peculiar  by  having  a  single  chitinous  rod  or  anchor- 
like  structure  known  as  a  breast-bone,  which  serves 
to  scrape  the  plant  tissue  on  which  the  creature  feeds. 
These  gall-midges  or  Cecidomyiids  attack  a  great  va- 
riety of  plants  at  all  sorts  of  points,  and  cause  a  great 


FIG.  33. — The  pear  midge,  Diplosis  pyrivora:  a,  female  adult;  c,  pupa;  other 
references  to  structural  details. 


variety  of  deformations  that  are  commonly  known 
as  galls,  although  they  differ  totally  in  character  from 
the  galls  caused  by  the  Cynipids.  For  instance,  the 
pear  midge  lays  its  eggs  in  the  pear  blossom;  the 
larvae  enter  the  seed  capsule  of  the  fruit  and  the  latter 
becomes  somewhat  abnormal  in  shape  so  that  to  the 
practised  eye  the  galling  is  perceptible.  The  Hessian 
fly  lays  its  egg  in  the  sheath  of  the  wheat  leaf  near 
6 


82  INSECTS 

the  ground;  the  larva  starts  its  feeding  there  and 
causes  an  injury  which  the  plant,  in  its  efforts  to  repair, 
marks  by  an  enlargement.  A  midge  lays  its  eggs  in 
the  tip  of  a  willow  shoot,  the  larvae  feed  at  the  base 
of  the  forming  leaves  and  the  plant  becomes  crippled, 
producing  a  cabbage-like  head  instead  of  a  shoot  with 
developed  foliage.  And  so  we  have  every  gradation 
from  a  feeding  without  any  perceptible  enlargement 
or  swelling  at  all,  to  a  well-formed  abnormity  formed 
by  a  crippling  of  the  natural  growth,  and  not  a  distinct- 
ly separate  structure,  unrelated  to  normal  growth. 
There  are  other  types  of  midge-galls,  like  those  on  the 
grape,  which  are  mere  fleshy  swellings  of  the  normal 
tissue,  and  sometimes  more  characteristic  enlargements 
of  infested  twigs;  but  generally  no  separable  galls. 

As  to  the  actual  injury  caused,  that  varies  enor- 
mously. Many  of  the  midge-galls  cause  no  real  or  per- 
manent injury  whatever  to  the  plant  attacked.  Others 
destroy  either  the  plant  or  the  seed  beyond  all  chance 
of  recovery.  These  midges  are  to  be  accounted  among 
the  most  serious  plant  enemies,  although  soft  her- 
baceous plants  and  grasses  are  more  apt  to  suffer; 
very  few  of  them  occurring  in  genuinely  woody  tissue. 

Among  the  Muscid  flies  resembling  in  general  type 
and  appearance  the  house-flies,  the  An  thorny  iids  are 
the  most  troublesome  and  dangerous.  They  attack 
a  very  great  variety  of  plants  and  may  be  miners  in 
the  thick  leafed  forms  like  beets,  or  feeders  in  roots 
like  those  of  the  radish,  cabbage  or  onion.  And  these 
root  maggots  are  very  generally  fatal  to  the  plant 
attacked,  so  that  their  rank  as  .destroyers  is  high. 
The  maggots  themselves  differ  very  little  from  the 
other  Muscid  larvae;  in  fact  not  at  all  to  ordinary  view, 
and  they  gain  their  food  in  the  same  way  by  scraping 
and  disintegrating  the  tissue  and  then  absorbing  the 


THEIR  RELATION  TO  PLANTS  83 

liquid  mess.  There  is,  in  consequence,  nearly  always 
an  appearance  of  decay  associated  with  the  work  of 
such  maggots,  and  that  appearance  is  very  real  in 
cases  where  the  wounded  surface  gives  entrance  to 
soft  rots  of  various  sorts.  As  for  the  leaf  miners,  their 
work  is  not  so  destructive  in  character,  although  natur- 
ally every  injury  that  impairs  the  usefulness  of  the  foli- 
age to  the  plant,  reacts  upon  the  entire  organism  to 
some  extent. 

There  are  other  maggot-like  larvae  that  work  in 
plant  or  fruit  tissue  such  as  the  apple  maggot,  the 
orange  fruit  fly  and  a  considerable  number  of  other 
fruit  flies  which,  while  they  seriously  affect  the  com- 
mercial value  of  the  product,  do  absolutely  no  injury 
to  the  plant,  since  neither  the  seed  nor  the  tree  itself 
is  affected.  Only  the  pulpy  covering  to  the  seed  is 
harmed  and  that  is  of  no  importance  at  all  to  the  plant 
however  much  it  may  be  to  man. 

We  have  thus  reviewed  very  briefly  the  various 
orders  of  insects,  and  have  called  attention  very  cur- 
sorily to  the  kind  of  injury  which  is  caused  by  them. 
From  the  time  it  appears  above  ground  to  the  period 
of  maturity,  almost  every  species  of  plant  serves  as 
food  for  insects;  and  if  it  survives  their  various  as- 
saults and  reproduces  its  kind,  its  decay  and  return 
to  the  inorganic  constituents  from  which  it  made  its 
growth  is  hastened  by  yet  other  species.  And  that 
applies  as  much  to  the  forest  giant,  aged  hundreds  of 
years,  as  to  the  humble  cabbage  plant  that  runs  its 
course  in  a  single  season. 


CHAPTER  IV 

THEIR  RELATION  TO  EACH  OTHER 

IT  has  been  brought  out,  directly  and  incidentally, 
that  insects  are  among  the  most  prolific  animals.  If  all 
the  feeders  on  vegetable  life  were  allowed  to  develop 
absolutely  without  check  during  two  successive  years, 
the  first  of  them  would  see  every  green  thing  swept 
from  the  face  of  the  earth,  and  the  second  would  destroy 
all  possibility  of  the  future  recurrence  of  fully  90  per 
cent,  of  all  the  existing  plants.  And  if  during  the  same 
period  all  forms  feeding  upon  vertebrate  life  were 
allowed  to  develop  in  the  same  way,  our  globe  would 
be  a  practically  uninhabited  and  uninhabitable  desert. 

But  the  very  fact  that  they  are  so  remarkably 
fecund  is  an  indication  that  they  have  many  dangers 
to  contend  with  and  many  difficulties  to  surmount 
before  reaching  the  adult  or  reproductive  stage.  Under 
normal  conditions  and  in  the  long  run,  one  pair  of 
moths,  producing  say  500  eggs,  are  represented  next 
year  by  another  pair  of  the  same  species,  and  no  more: 
that  is,  out  of  500  eggs,  producing  500  caterpillars, 
498  are  destroyed  in  some  way.  Naturally  this  varies 
from  year  to  year  to  some  extent,  favorable  conditions 
permitting  an  increase  one  year  and  causing  a  decrease 
at  some  other  period.  And,  equally  of  course,  while 
some  broods  may  be  completely  destroyed,  others 
may  all  come  to  maturity. 

Now  the  very  fact  that  an  insect  exists  at  all,  is 
proof  that  it  is  adjusted  to  its  surroundings,  including 
its  parasitic  and  predatory  enemies  and  all  the  other 
natural  checks.  And  when  it  occurs  as  an  abundant 

84 


THEIR  RELATION  TO  EACH  OTHER        85 


Ovarian 
\Jubesmth 

eggs 


species  it  means  that  this  abundance  is  normal,  and 
that  the  natural  adjustments  are  such  as  to  maintain 
that  abundance  in  relation  to  its  food  unless  man  in- 
terferes, and  the  results  of  such  interference  will  be  the 
subject  of  further  discussion,  later.  The  important 
point  is  that  a  species  abundant  in  number  of  specimens 
has  become  so  in  spite  of  the  combination  of  all  its 
natural  checks  and,  condi- 
tions remaining  equal,  will 
maintain  itself  in  the  same 
ratio,  just  as  a  rare  species 
barely  maintains  itself 
against  the  combination  op- 
posing it.  It  happens  again 
and  again  that  a  common 
species  becomes  more  than 
usually  abundant,  and  it  oc- 
curs occasionally  that  a 
species  normally  rare  escapes 
from  its  control  and  makes 
its  mark  as  an  injurious 
form.  But  even  without 
human  interference  this 
rights  itself  in  a  season  or 
two:  the  common  species 

may  even  be  reduced  for  a  time  to  less  than  its  usual 
numbers,  while  the  rare  species  drops  back  out  of  sight 
of  all  but  the  collector.  The  checks  or  natural  enemies 
of  neither  form  ever  increase  sufficiently  under  normal 
conditions  to  do  more  than  restore  the  original  ratio. 
What  then  are  these  checks  that  prevent  with  such 
absolute  effect  any  undue  increase  of  a  species  despite 
enormous  reproductive  powers?  They  are  really  very 
numerous  and  of  decidedly  unequal  effect  on  the  dif- 
ferent forms.  We  have  weather,  disease,  insectivorous 


FIG.  34. — Ovaries  of  a  bee  show- 
ing the  different  parts. 


86  INSECTS 

animals  of  many  species,  birds  and,  last  but  by  no  means 
least,  in  the  war  of  insect  upon  insect,  the  predatory 
and  parasitic  forms.  It  was  almost  inevitable  that 
in  the  course  of  development  some  originally  plant- 
feeding  insect  would  find  itself  in  position  to  get  its 
plant  juices  at  second  hand,  so  that,  instead  of  feeding 
upon  plant  tissue  directly,  it  fed  upon  its  next  neighbor 
and  got  the  same  material  indirectly.  We  have,  even 
now,  examples  in  Hemiptera  and  Coleoptera  of  species 
that  feed  upon  vegetable  tissue  and  also  upon  other 
insects  when  they  get  in  the  way;  or  of  species  which, 
while  normally  predatory,  occasionally  feed  upon 
vegetation.  In  the  Hemiptera  I  know  of  examples  of 
this  kind  in  the  Pentatomida  and  in  Coleoptera  they 
occur  in  the  Carabidce  and  Coccinellidce.  And  the 
step  from  predatory  to  parasitic  habits  is  an  easy  one, 
albeit  a  much  greater  specialization.  Insect  feeders 
upon  vegetable  life  were  first  developed;  predatory 
forms  came  very  soon  afterward  and  occur  in  almost 
if  not  quite  all  orders;  parasitism  on  other  insects 
came  much  later,  and  is  best  developed  in  the  highest 
and  most  specialized  orders,  being  practically  non- 
existent in  the  lower  or  primitive  types.  Parasites 
on  higher  animals,  such  as  the  biting  and  sucking  lice 
which  occur  in  the  Neuroptera  and  Hemiptera,  are  not 
in  any  way  comparable  with  the  insect  parasites  that 
occur  in  the  Hymenoptera  and  Diptera,  to  which  highly 
specialized  and  most  recently  developed  orders  the 
great  majority  of  all  the  parasites  on  insect  life  belong. 
There  are  few  true  parasites  in  any  other  of  the  orders. 
Among  the  Thysanura  we  have  no  parasites  and  no 
predatory  forms.  In  the  Neuroptera  we  have  many 
decidedly  predatory  forms  and  the  beginnings  of  par- 
asitism. The  Neuroptera  as  limited  in  Chapter  I,  con- 
sists of  a  number  of  remnants  of  earlier  types,  agreeing 


THEIR  RELATION  TO  EACH  OTHER        87 

only  in  the  fact  that  the  wings  have  numerous  longi- 
tudinal and  transverse  veins,  breaking  them  up  into 
many  small  areas  so  as  to  appear  more  or  less  netted. 
But  in  the  detailing  of  habits  and  suggesting  lines  of 
descent,  further  subdivision  is  convenient. 

Thus  the  Ephemerida  or  May-flies  contain  neither 
parasitic  nor  predatory  forms.  In  the  larval  or  early 
stages  they  live  in  the  muddy  bottom  of  streams,  feed 
on  the  organic  life  contained  in  this  material  and,  in 
the  adult  stage,  do  not  feed  at  all.  Yet  it  is  here  that 
the  highest  orders  get  their  start  and  in  them  predatory 
and  parasitic  types  are  numerous. 

In  the  Plecoptera  or  stone-flies  we  have  a  similar 
record  except  that  the  mouth  structures  in  all  stages 
are  much  better  developed.  Here  the  larval  stages 
are  passed  under  submerged  stones,  usually  in  running 
streams,  and  the  food  consists  of  such  floating  organic 
material  as  is  carried  in.  The  adults  in  s/pite  of  their 
rather  well-developed  mouth  organs  have  not  been 
observed  feeding. 

The  Mallophaga  or  biting  lice  are  animal  parasites 
and  are  dealt  with  in  Chapter  VII,  and  the  Corrodentia 
or  book-  and  bark-lice  are  feeders  on  dry  or  dead  or- 
ganic matter;  not  really  scavengers,  but  nevertheless 
removers  of  dead  material. 

The  order  Isoptera,  containing  the  Termites  or 
white  ants,  is  interesting  from  its  communal  life  and 
will  be  referred  to  again;  but  it  depends  entirely  upon 
vegetable  matter  for  its  subsistence  and  mainly  upon 
dead  tissue. 

The  order  Platyptera  is  the  first  of  the  Neuropterous 
types  to  contain  predatory  forms  and,  while  it  is  aquatic 
like  the  Plecoptera,  has  the  metamorphosis  complete  and 
is  altogether  much  better  developed,  albeit  the  adults 
are  loose- join  ted  and  flabby  enough,  when  handled. 


88 


INSECTS 


The  larvae  have  the  jaws  and  other  mouth  parts  well 
developed  and  feed  upon  other  soft-bodied  aquatic 
forms.  They  assist  in  checking  the  increase  of  the 
May-flies  and  stone-flies,  and  are  themselves  hunted 
by  fish,  which  keep  them  down  to  normal  numbers. 


CL 


FIG.  35. — The  " hellgrammite "  or  "Dobson":  a,  larva;  b,  pupa;  c,  male  adult; 
d,  head  of  female. 

The  order  Neuroptera,  strictly  speaking,  contains 
only  predatory  forms  and  the  beginning  of  parasitic 
habits.  With  few  exceptions  the  species  are  terrestrial. 
The  families  Coniopterygidce,  Chrysopidce ,  Hemerobiidcz 
and  Myrmeleonida ,  are  rather  similar  in  the  larval 


THEIR  RELATION  TO  EACH  OTHER        89 

stage;  the  body  being  more  or  less  ovate,  set  with 
lateral  tubercles  giving  rise  to  groups  of  bristles,  while 
the  mandibles  are  long,  slender  and  pointed,  peculiar 
in  being  grooved  on  the  inner  side  so  that  the  body 
juices  of  the  prey  may  run  down  through  them  into  the 
mouth  cavity.  The  Chrysopidce  are  known  as  Aphis- 
lions,  and  when  they  capture  a  plant  louse  it  is  held 
up,  impaled  on  the  mandibles,  until  the  juices  are  all 


FIG.  36. — A  lace-wing  fly,  Chrysopa  oculata:  a,  eggs  on  stalks;  b,  larva;  d,  same 
feeding  on  pear  psylla;   e,  the  cocoon  from  which  /,  the  adult,  has  escaped. 

absorbed;  then  the  dry  carcass  is  thrown  away.  The 
Myrmeleonidce  or  ant-lions  build  a  pit  in  the  sand  to 
entrap  any  unwary  insect  that  may  come  along,  and 
anything  that  does  come  is  seized  in  the  same  way  and 
exhausted,  the  empty  shell  being  thrown  out  later. 
Not  all  ant-lions  build  pits  and  not  all  the  members  of 
the  families  named  agree  in  all  respects  with  the  general 
statements  as  to  larval  form  and  characters;  but  for 
the  majority  of  the  species  that  come  under  observa- 
tion they  are  correct. 


90  INSECTS 

The  Raphidiidcc  are  very  curious  creatures  peculiar 
to  the  Pacific  Coast,  in  which  the  head  and  prothorax 
of  the  adult  are  greatly  elongated  and  it,  as  well  as 
the  slender  elongated  larva,  is  predatory.  In  the  pre- 
ceding families,  while  the  larvae  are  voracious  feeders, 
the  adults  feed  little  or  not  at  all. 

The  Mantispida  are  similar  to  the  Raphidiidce  in 
the  elongation  of  the  prothorax;  but  the  head  is  much 
shorter  and  the  fore  legs  are  enormously  developed 
for  grasping,  this  series  being  also  predatory  in  the 

adult  stage.  But  the  interest- 
ing feature  is  that  we  find  in 
the  larva  the  first  tendency 
toward  parasitism  and  the 
specializations  accompanying 
it.  The  eggs  are  laid  on  stalks 
like  those  of  the  Aphis-lions, 
but  the  resulting  young  live 
for  months  without  food,  until 
FIG  37.  —  Mantispa  species  the  egg  sacs  of  certain  Lycosid 

from  above  and  in  outline  from 

side.  spiders   have  been   formed. 

The    lucky    larva    that     finds 

such  a  sac  bites  its  way  through  the  covering  and  feeds 
upon  the  contents.  As  it  feeds  and  grows  it  loses  its 
large  head  and  long  legs,  and  becomes  helpless  except 
to  feed  upon  the  surrounding  material  which  serves 
to  bring  it  to  maturity.  While  in  a  general  way  these 
insects  are  said  to  be  parasitic  in  the  egg  sacs  of  spiders 
yet  this  is  not  really  a  true  parasitism  at  all;  it  is 
simply  a  feeding  upon  the  eggs  and  young  spiders  as 
any  predatory  species  might  feed  upon  them,  the  only 
difference  being  that  here  the  larva  makes  itself  at 
home  and  does  its  feeding  gradually,  so  as  to  secure 
enough  to  reach  maturity. 

The  order  Mecoptera  is  a  curious  one,  only  a  few 


THEIR  RELATION  TO  EACH  OTHER        91 

genera  and  species  remaining  as  representatives  in 
our  fauna.  All  of  them  are  feeders  on  animal  matter 
and  most  of  them  are  predatory  in  all  stages.  The 
best  known  forms  are  the  scorpion  flies,  so  called  from 
the  curious  anal  appendages  of  the  male,  which  bear  a 
remote  resemblance  to  a  scorpion  tail  without  its  ter- 
minal sting.  The  larvae,  which  are  somewhat  caterpillar- 
like,  live  under  ground  and  prefer  rather  damp  places. 
There  are  not  enough  of  the  insects  to  make  them  of 
any  importance  as  checks  to  anything  in  particular, 


FIG.  38. — A  Panorpa  or  scorpion  fly  and  its  larva. 

and  as  they  feed  rather  indiscriminately  on  soft-bodied 
insects,  chiefly  flies,  they  are  of  no  economic  value. 
It  is  probable  that  this  order  represents  the  type  from 
which  the  Diptera  and  Hymenoptera  were  derived. 

The  caddice  flies  or  Trichoptera  are  aquatic  in  the 
larval  stages  and  as  aerial  adults  do  not  feed  at  all. 
As  larvae  they  derive  their  name  from  their  habit  of 
making  cases  or  "caddices"  of  various  shapes  from 
little  sticks  or  stones  closely  fitted  and  held  together 
with  silk.  Some  of  the  species  are  feeders  upon  vege- 
table matter,  others  appear  to  be  predatory,  or  feeders 
upon  animal  matter  at  least.  They  are  very  numerous 
in  specimens  and  species,  but  naturally  do  not  influence 


92  INSECTS 

any  terrestrial  forms.  The  adults  have  the  wings 
covered  with  fine  hair  and  some  of  the  small  forms 
resemble  Tineid  moths  so  closely  that  they  are  con- 
fused with  them.  It  is  believed,  indeed,  that  this  is 
the  direct  ancestral  form  of  the  Lepidoptera. 

And  now  comes  the  order  Odonata,  containing  the 
dragon  flies,  large  and  small  and  all  of  them  predatory 
in  habit  in  all  stages.  As  larvae  they  are  aquatic,  living 
in  ponds,  streams  or  even  the  more  permanent  pools 


FIG.  39. — Dragon  fly  and  its  development:  larva  and  pupa  feeding  at  i  and 
3;  2,  nymph  ready  to  change;  4,  pupa  skin  from  which  5,  the  adult,  has  emerged. 


and  puddles;  some  of  them  active,  moving  about 
freely  among  the  vegetation,  others  sluggish,  lying  in 
the  soft  bottom  mud  or  under  stones  or  other  shelter, 
waiting  for  things  to  come  their  way.  They  are  pecu- 
liarly adapted  by  their  elongated  hinged  under  lip, 
or  labium,  to  reach  such  small  creatures  as  fate  may 
send  within  half  an  inch  of  them  and,  with  a  little  for- 
ward jerk  of  .  the  body  and  a  rapid  extension  of  the 
armed  labium,  the  prey  is  seized.  This  prey  varies  in 
character  according  to  the  habits  of  the  larvae.  Some 
of  the  more  active  forms  destroy  a  large  number  of 


THEIR  RELATION  TO  EACH  OTHER        93 

mosquito  wrigglers  and  display  surprising  skill  in  cap- 
turing them.  Others  take  in  anything  that  comes  along, 
be  it  insect,  crustacean,  or  even  small  pollywog  or  fish. 
They  have  no  aversion  to  their  own  kind  and  will  eat 
each  other  if  food  is  scarce  or  not  easily  obtainable. 
As  for  the  adults,  anything  that  comes  within  their 
range  will  answer  as  prey ;  but  in  general  small  flies  are 
the  most  abundant  victims.  The  common  name  "mos- 
quito hawk"  indicates  one  common  article  of  food, 
and  there  is  no  doubt  that  a  very  large  number  of 
specimens  is  eaten.  In  some  cases  the  mosquito  pest 
may  even  be  materially  lessened  by  them  during  the 
period  of  adult  flight;  but  they  scarcely  rank  among 
the  really  controlling "  checks  because  they  are  active 
only  during  the  day  while  the  mosquitoes  prefer  the 
night  for  their  flight;  and  the  dragons  prefer  the  open 
sunlit  area  around  ponds  or  along  streams,  while  those 
mosquitoes  that  fly  at  all  during  the  day  prefer  shel- 
tered, shaded  and  darkened  places.  Most  of  the  dragon 
flies  are  simply  general  predatory  feeders  on  any  soft- 
bodied  insects  which  they  can  overtake,  rather  than 
specific  enemies  of  any  one  form. 

In  the  order  Hemiptera  there  are  no  parasites  on 
insect  life.  The  lice,  parasitic  on  vertebrate  animals, 
are  elsewhere  considered,  and  nowhere  else  do  we  find, 
in  this  order,  any  approach  to  true  parasitism.  Of 
predatory  forms  there  are  a  large  number;  indeed 
among  the  aquatic  species  the  majority  are  predatory, 
feeding  on  other  water  insects  and  even  fish.  Among 
these  the  little  Corisidce  and  N otonectidce ,  water-boatmen 
and  back-swimmers,  are  especially  vicious  and  active, 
easily  forming  a  very  notable  factor  in  the  control  of 
aquatic  insect  life. 

Among  the  terrestrial  forms  the  entire  series  Hom- 
optera  lacks  predatory  types;  in  the  Heteroptera  we 


94 


INSECTS 


find  that  modification  of  habit  which  is  elsewhere  re- 
ferred to — a  tendency  to  get  plant  juices  at  second 
hand,  by  sucking  the  juices  of  such  soft-bodied  larvae 
as  have  just  fed  upon  plant  tissue.  This  is  found  in 
quite  a  large  number  of  the  families,  making  a  con- 


FIG.   40. — The  wheel-bug,  Prionidus  cristatus,  in  all  its  stages. 


siderable  series  of  species  that  feed  indifferently  on 
plant  or  soft  insect  tissue.  But  there  is  also  a  large 
number  of  species  with  short  stiff  beaks  and  small 
narrow  heads  that  are  distinctly  and  exclusively  pred- 
atory. These  are  the  Reduviida  commonly  known  as 
"  pirate  "  or  "  assassin  bugs  "  from  their  habit  of  stabbing 
or  piercing  the  specimens  upon  which  they  feed. 


THEIR  RELATION  TO  EACH  OTHER        95 

These  bugs  are  of  considerable  importance  as  checks 
to  certain  plant  feeders  and  as  they  feed  in  the  same 
way  throughout  their  life,  each  individual  accounts 
for  a  notable  number  of  victims.  Their  weak  point 
is  the  limited  power  of  reproduction.  Most  of  them 
lay  only  a  small  number  of  eggs  and  have  only  a  single 
or  at  most  two  broods  during  the  season.  As  a  control 
factor,  therefore,  they  lack  flexibility  and  do  not  rise 
to  any  sudden  increase  in  the  plant  feeders.  There  is 
a  common  species  that  in  New  Jersey  feeds  on  the 
larvae  of  the  elm-leaf  beetle,  and  each  season  is  busily 
engaged  on  the  infested  trees  in  fair  numbers.  In 
years  when  the  beetle  is  not  abundant  the  marks  of 
its  feeding  are  quite  conspicuous;  but  in  a  season  when 
the  beetle  is  unusually  plentiful  and  destructive,  the 
bugs  are  present  in  almost  exactly  the  same  numbers 
and  their  work  is  absolutely  unnoticeable  when  effec- 
tiveness is  most  urgently  needed,  nor  does  there  seem 
to  be  any  considerable  increase  during  the  season  fol- 
lowing such  an  abundance.  This  same  feature  exists 
with  most  of  the  species  known  to  me  and  limits  their 
usefulness  to  very  narrow  bounds;  they  constitute 
one  check  which  is  almost  a  fixed  quantity  and  to  which 
the  host  insects  are  adapted. 

The  order  Orthoptera,  including  roaches,  grass- 
hoppers, locusts,  crickets  and  the  like,  contains  no  true 
parasites  and  but  few  predatory  forms.  Some  of  the 
roaches  are  omnivorous  and  pick  up  occasional  speci- 
mens of  insects  and  animal  matter;  but  they  can 
scarcely  be  ranked  as  important  checks  to  any  other 
species.  And  so  the  Mantids  or  soothsayers  are  vora- 
cious feeders,  preying  upon  almost  any  sort  of  insects 
which  they  can  secure;  but  they  are  few  in  number 
both  as  to  species  and  specimens,  while  their  food  is 
so  various  that  they  are  not  of  importance  in  the  life 


96 


INSECTS 


cycle  of  any  one  kind.  Crickets  there  are  of  many 
sorts,  and  some  of  these  are  general  feeders,  eating 
each  other  as  freely  as  they  do  vegetation  and  other 
things.  The  tree-crickets  are  more  definitely  predatory 
in  habits  and  feed  largely  upon  plant  lice;  but  they 
also  are  too  few  and  too  slow  in  reproducing  to  be  able 
to  exert  a  very  important  influence  on  the  increase  of 
their  prey.  Furthermore,  they  are  limited  as  to  the 
places  which  they  inhabit,  and  no  field  crops  of  any 
sort  harbor  them. 


FIG.  41. — Stylops  and  its  development:    a,  female  in  body  of  bee;  b,  same  in 
outline;  c,  d,  male  from  above  and  side. 


In  the  order  Coleoptera  or  beetles  we  have  few 
truly  parasitic  forms.  We  may  for  the  present  consider 
the  family  Stylopidcz  as  true  Coleoptera  and  these  are 
found  in  the  abdomen  of  various  insects,  chiefly  bees 
and  wasps  although  some  Hemiptera  and  perhaps 
other  orders  are  also  infested.  But  they  are  so  very 
rare  that  they  exert  little  influence  on  the  numbers 
of  the  species  which  they  infest.  Their  life  history 
and  complicated  metamorphoses  are  extremely  inter- 
esting, the  female  being  wingless  and  living  in  the 
abdominal  cavity  of  its  host,  with  the  head  projecting 


THEIR  RELATION  TO  EACH  OTHER        97 

between  the  segments.  The  young  are  minute,  active 
creatures  like  those  of  the  blister  beetles,  and  run 
about  freely  until  they  find  some  suitable  host  in  which 
their  future  development  may  be  continued.  Then 
they  lose  their  feet  and  prominent  jaws,  becoming 
grub-like  and  inactive  as  the  necessity  for  seeking 
food  is  removed. 

The  blister  beetles  or  Meloida  are  semiparasitic 
in  habit  and  are  quite  numerous  in  specimens  and 
species.  Some  of  them  live  in  the  egg-pods  of  grass- 
hoppers and  others  in  the  nests  of  digger  bees,  chiefly 
Andrenidce,  feeding  on  the  food  stored  by  their  hosts 
and,  incidentally,  devouring  the  egg  or  young  larva 
of  the  bee.  These  blister  beetles  will  be  referred  to 
again  in  their  relation  to  man,  but  in  their  relation  to 
the  insects  upon  which  the  larvae  feed  they  rank  as  most 
effective  checks.  The  female  beetle  lays  her  eggs  on 
flowers  or  on  the  ground  as  the  case  may  be,  and  the 
resulting  larvae  are  active  creatures  with  long  legs 
and  large  jaws  known  as  "  triungulins. "  These  are 
able  to  go  for  long  periods  without  food  and  they  seek 
either  a  grasshopper  egg-pod  or  some  plant  or  flower 
frequented  by  bees,  as  the  need  may  be.  The  forms 
that  hunt  egg-pods,  when  they  succeed  in  finding  one, 
immediately  begin  to  feed.  The  forms  that  wait  for 
bees  attach  themselves  to  almost  any  hairy  insect 
that  comes  along  and  the  lucky  specimen  that  gets 
upon  a  bee  of  the  right  kind  is  carried  by  it  into  its 
burrow.  When  the  bee  with  its  burden  of  pollen  plus 
the  parasite  gets  into  the  cell  which  it  is  filling  with 
food  for  its  larva,  the  triungulin  slips  off,  devours  the 
egg  of  its  host  as  soon  as  laid,  and  that  suffices  to 
bring  it  to  the  end  of  the  first  stage.  From  this  point 
the  changes  in  both  kinds  of  larvae  are  similar.  They 
are  in  direct  contact  with  abundant  food,  the  legs 
7 


98 


INSECTS 


and  large  jaws  are  useless  and  they  enter  what  is  known 
as  the  "Carabidoid"  stage  in  which  they  resemble  the 
larvae  of  ground  beetles.  Continued  good  feeding  re- 
sults in  a  further  reduction  of  parts  and  the  third  instar 
is  even  more  grub-like  and  therefore  termed  the  "Scar- 
abidoid"  stage,  during  which  it  exhausts  its  food  sup- 
ply,—either  the  egg-pod  or  the  stored  material  in  the 


FiG.,42. — Development  of  a  blister  beetle:  a,  grasshopper  egg  pod  with  tri- 
ungulin  at  //  b,  a  few  grasshopper  eggs;  c,  triungulin;  d,  carabidoid  larva;  e, 
scarabidoid  larva. 


bee  cell.  Then  the  outer  skin  hardens,  the  larva  loses 
shape  and  enters  the  coarctate  stage  in  which  it  lies 
dormant  until  the  period  when  the  adult  is  due  to 
appear.  When  this  comes,  the  hardened  larval  skin 
is  shed  and  the  true  pupa,  of  the  ordinary  beetle  type, 
appears.  When  the  proper  hour  arrives,  as  if  at  the 
striking  of  a  clock,  the  transformation  to  the  adult 
is  completed  and  the  blister  beetles  emerge,  ready  to 
feed  and  propagate.  And  now  the  story  changes,  for 
while  we  can  have  only  words  of  praise  for  those  larvae 


THEIR  RELATION  TO  EACH  OTHER 


99 


that  feed  on  grasshopper  eggs,  the  adult  beetles  almost 
without  exception  are  devourers  of  plant  tissue.  Their 
habit  of  coming  to  maturity  at  about  the  same  time 
brings  clouds  of  them  upon  their  food  plants  at  once, 
and  gardens  and  certain  truck  crops  suffer.  It  becomes 
a  question  then,  whether  the  insects  are  economically 
more  useful  as  destroyers  of  grasshoppers  or  more 
destructive  as  feeders  on  crops.  As  to  the  species 
feeding  in  the  nests  of  bees,  they  are  without  question 
economically  injurious  in  all  stages. 


FIG.  43. — Two  common  blister  beetles:  a,  Macrobasis  unicolor;  b,  Epicauta 
Pennsylvania . 

But  there  can  be  no  doubt  either  that  in  regions 
where  grasshoppers  are  very  abundant,  as  they  are 
in  the  Rocky  Mountain  and  some  of  the  southwestern 
areas  of  the  United  States,  these  blister  beetles  are  a 
most  important  check  and  one  that  has  a  large  amount 
of  flexibility  in  effectiveness  despite  the  fact  that  there 
is  only  one  annual  brood.  This  is  obtained  by  the 
large  number  of  eggs  laid  by  the  female,  which  in  some 
species  runs  into  the  thousands.  The  adults  make  no 
attempt  to  place  these  near  egg-pods,  but  only  on 
ground  where  such  pods  are  likely  to  occur.  It  is  up 
to  the  young  larva  to  find  its  own  hotel  accommoda- 
tions or  starve  to  death.  When  grasshoppers  have  been 
scarce  and  pods  are  widely  scattered,  a  very  large  per- 


ioo  INSECTS 

centage  of  the  triungulins  never  get  beyond  that  stage; 
but  when  there  has  been  an  abundance  of  hoppers  and 
egg-pods  are  numerous,  matters  are  easier  for  the 
enemy  and  a  larger  percentage  secures  food.  In  this 
way  it  happens  that  after  a  season  of  grasshopper 
abundance  a  season  of  blister  beetle  abundance  is  al- 
most certain  to  follow,  and  any  abnormal  increase  of 
the  former  is  almost  sure  to  be  checked  by  the  cor- 
responding increase  of  the  latter. 

A  very  material  change  is  introduced  by  the  migrat- 
ing habit  of  some  of  the  host  species.  Blister  beetles 
are  not  great  travellers,  while  a  grasshopper  swarm 
may  fly  for  hundreds  of  miles,  clear  out  of  the  faunal 
range  of  their  check.  But  in  such  instances,  while 
they  may  have  a  year  or  two  of  unusual  freedom  for 
development,  they  become  in  time  victims  of  the  un- 
favorable climatic  conditions  in  their  new  surroundings 
and  are  crowded  back  into  their  natural  domains,  under 
the  control  of  their  normal  enemies. 

While,  in  a  way,  it  is  correct  to  refer  to  these  beetles 
as  parasitic,  they  are  not  really  more  so  than  the  Man- 
tispids  that  feed  in  spider  egg-sacs,  and  in  the  case  of 
those  feeding  in  the  cells  of  bees  they  are  even  less  so. 
For  here  the  egg  or  young  larva  of  the  bee  is  only  eaten 
to  remove  the  owner  of  the  stored  food  and  the  real 
object  of  the  "parasite"  is  the  stored  provender.  It 
is  therefore  a  robber  rather  than  a  parasite,  unless  we 
use  the  latter  term  in  a  very  broad  sense. 

As  to  predatory  forms,  the  order  Coleoptera  con- 
tains a  great  number.  All  those  species  that  have 
filiform  or  thread-like  antennae,  comprising  the  fami- 
lies Cicindelidce  (tiger-beetles),  and  Car  abides  (ground 
beetles),  Haliplidce  (diving  beetles),  and  Dytiscidce 
(water  tigers),  are  predominatingly  feeders  upon  other 
insects.  A  few  feed  on  vegetable  tissues  as  well  or  as 


THEIR  RELATION  TO  EACH  OTHER      101 

an  alternate,  and  a  very  few  seem  confined  to  a  plant 
diet;  but,  as  a  whole,  this  immense  series  of  species 
feeds  on  other  insects  in  both  larval  and  adult  stage. 
Most  of  them  are  rather  general  feeders,  taking  all 
things  that  come  in  their  way,  and  they  are  not  at  all 
particular  whether  this  prey  is  another  predatory  form 
or  a  plant  feeder.  And  we  have  species  that  frequent 
trees,  shrubs  and  flowers  as  well  as  those  confined  to 
the  ground:  the  smaller  forms  capable  of  feeding  only 
upon  eggs,  the  larger  climbing  trees  for  the  caterpillars 


FIG.  44. — A  caterpillar- hunting  ground 
beetle  and  its  larva. 


FIG.  45. — A  common  type 
of  ground  beetle. 


to  be  tound  on  them.  Some  of  the  species  have  the 
advantage  of  being  able  to  adapt  themselves  to  the 
conditions  found  in  cultivated  fields  and  orchards  and 
the  number  of  larvae  and  pupae  of  plant-feeding  forms 
that  go  under  ground  for  pupation  or  hibernation  that 
are  destroyed  by  them  is  beyond  all  computation. 
While  I  do  not  recollect  at  this  time  any  species  that 
devotes  itself  to  any  one  particular  kind  of  prey,  there 
is  no  sort  of  doubt  of  the  reality  of  the  check  which  the 
ground  beetles  exercise  over  the  increase  of  plant- 
feeding  forms— ^especially  those  which  pupate  on  or 
under  the  surface.  But  we  must  limit  this  praise  just 


IO2 


INSECTS 


a  little:  none  of  them  bother  with  such  small  fry  as 
plant  lice  and  scale  insects  and  their  cannibalistic 
habits  do  much  to  limit  their  usefulness. 

In  the  series  of  rove-beetles  or  StaphylinidG,  which 
are  scavengers  as  a  rule,  there  are  many  small  species 
that  are  predaceous,  and  what  a  battle  goes  on  between 
these  and  other  breeders  in  or  among  damp,  decaying 
vegetation  we  can  only  guess  when,  with  a  sieve,  we 
collect  out  of  a  handful  of  forest  leaves  sometimes  a 
dozen  species  of  adult  beetles  and  hundreds  of  minute 
larvae   and   wriggling   creatures  of 
all  sorts.     The  collector  who  cov- 
ers a  dozen  miles  in  a  day  and  at 
night    has    a    box    of    butterflies, 
beetles  and  other  insects  to  show 
for  it,  has  seen  much;  but  he  has 
seen  nothing   of  the  intimate  life 
of  insects   as  compared  with    the 
man    who    has    spent    the    same 
period    in    an    open    glade    in    a 
deciduous  wood.     It  is  not  in  the 
open  air  and  on  the  surface  that 

the  most  interesting  matters  are  to  be  observed;  it  is 
under  the  shelter  of  fallen  leaves,  in  the  very  centre 
of  a  decaying  stump  or  log,  or  beneath  a  stone  and 
sometimes  deep  in  the  very  soil  that  insect  life  man- 
ifests itself  in  its  most  wonderful  ways.  It  means 
patient  watching  and  persistent  study  to  unravel  all 
these  mysterious  happenings  that  come  to  our  atten- 
tion, and  it  is  because  we  have  not  yet  done  enough 
of  this,  that  we  know  so  very  little  about  these  rove- 
beetles  and  their  minute  allies;  but  we  do  know  that 
they  are  not  all  scavengers  at  any  rate. 

Among  the  Coccinellidcz  popularly  known  as  "lady- 
birds,"    "ladybird    beetles"    or    simply     "ladybugs," 


PIG.  46. — A  rove-beetle 
and  its  larva. 


THEIR  RELATION  TO  EACH  OTHER      103 

we  find  a  very  decided  specialization  as  to  the  char- 
acter of  the  prey.  Almost  all  the  members  of  the  family 
are  predatory  during  the  larval  stage,  but  they  are  not 
general  feeders;  some  of  them  are  even  very  closely 
limited  as  to  food,  and  form  specific  checks  of  the  very 
highest  importance.  Remove  one  of  these  checks  and 
the  host  may  become  immeasurably  destructive:  re- 
store it  and,  no  matter  how  much  the  host  has  gained, 
the  check  will  regain  control.  Plant  lice  and  scale 
insects  are  the  especial  prey  Df  these  beetles  and  the 
facts  just  recited  are  within  the  observation  of  almost 
every  student  of  entomology.  We  are  in  the  habit  of 
thinking  of  "ladybird  beetles"  as  being  red  or  yellow 
in  color  with  black  spots,  and  as  nearly  hemispherical 
or  at  least  convexly  oval  in  form.  The  form  is  quite 
constant  indeed,  but  the  colors  are  by  no  means  all 
gay.  Besides  the  red,  yellow  and  black  species  there 
are  those  that  reach  to  metallic  blue  and  yet  others 
that  are  dull  or  shining  black  with  very  little  if  any 
maculation.  The  variation  in  size  is  also  considerable, 
for  while  we  have  giants  half  an  inch  in  length,  we 
have  Mso  midgets  not  much  more  than  one  one-hun- 
dredth of  an  inch  over  all. 

Is  there  any  unusual  increase  of  a  plant  louse  or 
scale  species:  in  a  few  weeks  their  ladybird  enemies 
will  be  found  to  be  on  the  increase  as  well,  and  very 
often,  even  before  the  end  of  the  season,  the  control 
will  be  re-established;  for  many  of  these  species  have 
several  broods  during  the  year  and  plenty  of  food  is 
conducive  to  quick  development.  Even  a  normally 
rare  species  may  under  such  a  spur  become  abundant. 
An  example  of  such  control  I  have  seen  on  several 
occasions  in  the  case  of  a  plant  louse  that  infests  Nor- 
way maples,  by  the  i5~spotted  ladybird,  which  is  not 
usually  common.  When  weather  conditions  during 


IO4 


INSECTS 


early  spring  favor  the  plant  lice  they  increase  until 
June,  when  the  first  hot,  dry  spell  puts  a  period  to  their 
work.  An  unusually  cold,  wet  spring  will  be  accom- 
panied by  an  unusual  abundance  of  lice,  and  on  three 
occasions  within  twenty  years  when  the  cold,  wet 
weather  extended  into  late  June,  infestation  became 
so  serious  that  the  leaves  were  covered  with  honey- 
dew  and  soot-fungus,  so  that  they  choked  and  began 

to  drop.  But  about  this 
time  the  ladybirds  were 
also  in  the  running  and 
had  become  so  numerous 
that  they  were  fast  reduc- 
ing the  plant  lice  and  put- 
ting a  period  to  the  infes- 
tation. And  then  came  the 
long  deferred  hot  spell  in 
early  July,  wiping  out  the 
plant  lice  as  with  a  sponge 
and  leaving  thousands  of 
beetle  larvae  without  food. 
What  did  they  do?  First 
the  larvae  ate  all  the  eggs 

of  their  own  kind  yet  on  the  leaves;  then  they  ate  the 
helpless  pupae  getting  ready  to  change  to  the  adult  stage ; 
then  the  large  larvae  ate  the  smaller  ones  and  as  they 
became  full  fed  and  pupated,  they  in  turn  became  vic- 
tims to  those  that  had  escaped  the  slaughter.  And  before 
the  end  of  July  the  15 -spotted  ladybird  beetle  was  again 
a  rare  insect  and  no  outward  sign  remained  to  tell  what 
crowds  of  them  had  been  on  the  scene  a  month  before. 
But  not  all  Coccinellids  are  able  to  increase  so 
rapidly;  some  species  being  strictly  limited  to  one 
brood.  The  cottony  maple  scale  in  the  east  is  con- 
trolled by  the  signate  ladybird,  Hyperaspis  signata, 


FIG.  47. —  is-spotted   lady-beetle:  a, 
larva;  b,  pupa;  d-g,  adult  varieties. 


THEIR  RELATION  TO  EACH  OTHER      105 

a  little  black  species  with  one  red  spot  on  each  wing- 
cover.  About  once  every  decade  the  scale  escapes  con- 
trol, and  for  a  series  of  three  or  four  years  becomes  in- 
creasingly abundant  so  that  tree  owners  are  thoroughly 
scared  and  demand  remedial  measures.  Experience 
has  enabled  me  to  assure  these  owners  that  when  mat- 
ters are  apparently  getting  serious,  the  worst  is  over; 
because  by  the  end  of  the  third  year  the  Hyperaspis 
has  caught  up  with  its  host  and  almost  every  scale 


FIG.  48.— The  signate  lady-beetle. 

egg  mass  contains  one  or  more  beetle  larvae  feeding  in 
and  upon  it.  The  year  following,  scales  may  be  difficult 
to  find  and  the  Hyperaspids  are  forced  to  other  species 
upon  which  they  fail  to  maintain  themselves  and 
perish — all  save  a  few  that  find  enough  congenial  food 
to  maintain  the  species. 

What  happens  when  an  insect  of  this  character  is 
entirely  freed  from  its  normal  check,  was  demonstrated 
in  California  when  the  cottony  cushion  scale,  I  eery  a 
purchasi,  was  introduced  from  Australia  without  the 
Vedalia  cardinalis.  In  a  few  years  the  Icerya  had  as- 


io6  INSECTS 

sumed  the  dimensions  of  a  calamity  and,  as  one  excited 
grower  informed  me,  even  the  hitching  posts  became 
infested.  The  introduction  of  the  ladybird  enemy 
which  had  been  discovered  in  the  native  home  of  the 
scale  turned  the  tables  at  once.  In  less  time  than  it 
had  taken  the  scale  to  overrun  the  country,  the  Vedalia 
aided  by  artificial  breedings  and  distribution,  cleaned 
it  out,  until  now  both  scale  and  beetle  barely  maintain 
themselves.  There  are  undoubtedly  many  other  similar 
relations,  but  on  this  point  we  have  yet  much  to  learn. 
It  rarely  happens  that  a  Coccinellid  beetle  ranges 
far  from  its  normal  food  or  a  very  closely  allied  species, 
and-  however  flexible  and  adaptable  it  may  be  in  rela- 
tion to  its  normal  prey,  it  generally  fails  when  pitted 
against  an  unknown  or  new  form.  The  San  Jose  or 
pernicious  scale  is  a  rather  close  ally  of  several  of  our 
native  armored  scales,  and  the  Coccinellids  that  feed 
upon  these  also  attack  this  introduced  form;  but  east 
of  the  Rocky  Mountains  none  of  them  exercise  the 
least  real  control  over  it.  On  the  Pacific  Coast  the 
Chilocorus  bivulnerus  or  twice-stabbed  ladybird  does 
act  as  an  effective  check  because,  having  several  broods 
during  the  season,  it  becomes  plentiful  enough  to  de- 
vour a  large  percentage  of  the  hibernating  forms.  In 
the  east  this  same  species  has  only  a  single  brood  and 
is  absolutely  impotent.  And  when  we  brought  in  the 
closely  allied  Asiatic  Chilocorus  similis  to  help  us  out, 
that  flourished  for  a  year  or  two  in  one  of  our  southern 
states  and  then  died  off.  In  the  more  northern  states 
it  never  gained  a  foothold  at  all.  The  little  Smilia 
misella,  native  to  the  Atlantic  states,  becomes  plenti- 
ful enough  at  times,  and  may  be  found  feeding  even  in 
midwinter;  but  while  it  undoubtedly  helps  to  keep 
down  numbers  somewhat,  it  cannot  be  considered  an 
effective  enemy. 


THEIR  RELATION  TO  EACH  OTHER      107 


And  so  we  have  in  these  Coccinellid  beetles  a  series 
of  the  most  highly  important  checks  to  some  of  the 
most  destructive  insect  types,  the  removal  of  which 
would  cause  a  serious  derangement  of  conditions  as 


FIG.  49. — Chilocorus  similis:  a,  beetle  laying  egg  under  scale;  b,  c.  scales 
showing  egg  in  place;  d,  egg  in  scale;  e,  egg;  /,  eggs  under  bark  flap;  g,  same, 
natural  size;  h,  i,  young  larvae;  /,  same  feeding. 


they  at  present  exist.  These  checks  are  flexible  within 
limits,  and  automatically,  by  simply  devouring  each 
other,  restore  themselves  to  inconspicuous  numbers 
when  their  services  are  no  longer  needed.  But  we  are 
not  yet  in  position  to  train  them  to  our  service  nor  to 
induce  them  to  feed  on  unfamiliar  species. 


io8 


INSECTS 


In  the  family  Lampyrida,  containing  the  fire-flies 
and  soldier  beetles,  and  among  the  flower  beetles  of 
the  families  Malachidcs  and  Cleridce,  we  have  a  series 
of  species  of  which  a  large  number  are  predatory  in 
the  larval  stages,  while  the  adults  are  feeders  on  pollen 
or  vegetable  tissue.  Among  the  fire-flies  some  of  the 
larvae  are  feeders  on  snails,  while  others,  with  those 
of  the  soldier  beetles,  are  limited  to  an  insect  diet. 
They  are  largely  found  on  the  surface  of  the  ground 
or  just  beneath  it,  and  they  get  a  great  many  of  the 
plant-feeding  forms  that  go  underground  to  pupate. 

Withal  they  are  rather  gen- 
eral feeders  and  not  specific 
checks.  Among  the  Clerida 
the  majority  of  the  species 
are  predatory  on  wood-boring 
forms,  and  some  of  them  are 
specific  checks  on  the  bark- 
boring  Scolytids.  The  larvae 
are  elongate,  rather  slender 
and  flattened  creatures  with 

a  large  head  and  prominent  jaws,  and  they  enter 
into  and  follow  the  galleries  of  their  prey,  which  is  un- 
able to  escape  and  absolutely  incapable  of  resistance. 
Under  normal  conditions  these  species  are  capable 
of  dealing  with  a  large  percentage  of  the  wood-borers; 
but  it  seems  rather  easy  to  turn  the  scale  against  them, 
and  the  Scolytids  often  do  a  great  deal  of  injury  when 
favored  by  careless  forest  practice,  fire  injury  or  other 
checks  to  tree  development.  Taken  as  a  whole  the  pred- 
atory and  semiparasitic  forms  among  the  beetles  are 
a  very  important  factor  in  keeping  down  plant-feeding 
forms  and  in  preventing  the  undue  increase  of  other 
species  which  are  not  directly  harmful  and  may  even 
be  beneficial. 


FIG.  50. — A  soldier  beetle  and 
its  larva. 


THEIR  RELATION  TO  EACH  OTHER      109 

The  order  Lepidoptera  contains  no  parasites  and 
very  few  species  which,  in  the  larval  stage,  are  preda- 
tory. In  the  adult  stage  the  mouth  structure  of  butter- 
flies and  moths  precludes  their  feeding  on  other  than 
liquid  food  where  they  feed  at  all.  A  very  few  of  the 
larvae  or  caterpillars  are  predatory,  feeding  on  scale 
insects  or  plant  lice.  Generally  speaking  these  insect- 
feeding  caterpillars  are  rare;  but  that  of  the  little 
Phycitid  Lcetilia  coccidivora  is  really  a  very  effective 
control  for  certain  of  the  soft  scales.  It  is  a  species 
that  belongs  to  the  same  series  as  the  flour  moths  and* 
meal  moths,  making  the  same  sort  of  silken  tube  as  a 
home;  only,  instead  of  webbing  together  kernels  of 
wheat,  etc.,  it  spins  up  a  mass  of  scales  and  feeds  upon 
the  eggs  or  young  even  before  they  have  issued  from 
beneath  the  mother  body. 

In  the  order  Diptera  we  have  a  very  interesting 
mixture  of  forms,  including  many  that  are  of  the  high- 
est importance  as  parasitic  or  predatory  checks  to 
other  species;  but  we  are  less  able  to  limit  these  species 
to  certain  families.  Here  we  may  have,  in  apparent 
close  relation,  species  that  as  larvae  are  plant  feeders, 
scavengers  and  true  parasites;  and  there  is  nothing 
in  the  adult  which  indicates  the  habit  of  the  larva, 
so  far  as  our  studies  have  yet  carried  us.  Even  in  the 
midges,  which  are  certainly  to  be  ranked  as  plant 
feeders,  there  are  a  few  that  have  been  credited  with 
feeding  on  certain  of  the  smaller  plant  lice.  Among 
the  Culicidaz  or  mosquitoes  there  are  a  number  of  larvae 
that  are  truly  predaceous,  and  a  few  of  them,  like  those 
of  Psorophora,  are  veritable  wolves  among  the  other 
wrigglers.  They  have  the  same  fault  that  I  have 
already  deplored  for  other  species : — they  limit  their  own 
increase  by  feeding  upon  their  brethren  when  other 
wrigglers  have  given  out. 


no 


INSECTS 


The  blood-sucking  flies  are  considered  in  another 
chapter  and  have  no  important  relation  to  other  in- 
sects, although  some  of  the  larvae,  notably  those  of 
the  Tabanidce,  or  horse-flies,  live  to  some  extent  on 
other  insect  larvae  inhabiting  swampy  and  marshy 
soil.  The  robber  flies  of  the  family  Asilidce  are  veritable 
falcons  of  the  insect  world  and  capture  their  prey  by 
pouncing  upon  it  in  flight,  sucking  its  juices  by  means 
of  their  powerful  battery  of  lancets,  and  then  discard- 
ing the  dry  husk.  They  are  not  at  all  particular  as  to 

what  sort  of  species  comes 
into  their  way, — a  fly,  a  bee, 
a  beetle  or  a  butterfly, — any- 
thing answers.  And  so  while 
they  devour  an  enormous 
number  of  specimens,  they  are 
not  specific  checks  to  any  line 
of  plant  feeders.  Indeed,  as  a 
matter  of  fact  the  robber  flies 
do  not  discriminate  in  the 
least:  they  will  as  cheerfully 
devour  a  dragon  fly  or  a 
ground  beetle  as  a  butterfly  or 
June-bug;  it  is  all  a  matter  of  which  comes  along  first. 
Among  the  bee-flies  or  Bombyliidce,  we  find  in  the 
larvae  both  parasitic  and  predatory  types,  and  forms 
which,  like  the  blister  beetles,  devour  the  stored  ma- 
terial of  bees  and  other  species.  The  adult  flies  them- 
selves are  often  bright  colored  and  hairy,  some  of  them 
resembling  bumble-bees  in  appearance  and  some  with 
long,  bee-like  mouth  parts.  In  the  larval  stage  some 
are  true  parasites  on  caterpillars,  notably  cut- worms, 
while  others  feed  in  the  egg-pods  of  grasshoppers, 
devouring  all  the  eggs  in  a  single  pod  in  attaining  full 
growth.  Those  that  feed  on  the  stored  food  in  bee 


FIG.  51. — A  robber  fly,  with  larva 
and  pupa. 


THEIR  RELATION  TO  EACH  OTHER      in 

cells  are  cuckoos  in  habit  and  are  effective  in  limiting 
bee  increase.  As  parasites  they  are  not  of  so  much 
importance,  for  while  they  do  their  share  in  limiting 
numbers  under  normal  conditions,  they  do  not  readily 
increase  in  abundance  when  the  host  becomes  un- 
usually plentiful.  Of  much  greater  importance  are 
those  species  that  depend  upon  grasshoppers;  for 
these  do  really  aid  in  effective  control,  the  larvae  in- 
creasing in  relative  numbers  as  the  egg-pods  themselves 


FIG.  52. — A  bee-fly  and  its  pupa. 


become  plentiful.  There  are  other  predatory  larvae 
among  the  Empidce  or  dance  flies  and  similar  small 
families;  but  none  of  any  great  importance,  until  we 
reach  the  Syrphidce  or  flower  flies.  Among  these  we 
find  a  large  number  that  are  specific  feeders  on  plant 
lice  and  among  their  important  checks. 

In  this  connection  it  is  interesting  to  note  that  in 
every  order  in  which  there  are  predatory  insects  at 
all,  there  are  some  that  feed  largely  or  exclusively  on 
plant  lice.  We  will  also  find,  in  another  connection, 
that  these  same  plant  lice  are  also  seriously  influenced 


ii2  INSECTS 

by  diseases  and  weather  conditions,  and  yet,  in  spite 
of  all  these  factors,  some  species  escape  from  their 
checks  almost  annually  to  the  greater  or  less  detriment 
of  the  plant  hosts.  And  they  always  maintain  them- 
selves as  against  all  these  combined  checks  even  when 
each  exercises  its  maximum  influence.  It  is  easily 
appreciable,  therefore,  that  when  one  or  two  of  these 
factors  fail,  e.g.,  weather  and  diseases,  as  not  infre- 
quently happens,  it  demands  a  great  increase  on  the 
part  of  the  other  checks  to  prevent  the  Aphids  from 


FIG.  53. — A  Syrphid  fly,  Mesograpta  polita. 

getting  out  of  hand  altogether.  The  Coccinellid  beetles 
have  been  already  referred  to  in  this  connection  and 
the  larvae  of  the  Syrphid  flies  make  a  very  good  second. 
The  flies  lay  their  eggs  in  the  very  midst  of  the  lice  and 
the  resulting  larva,  which  is  a  slug-like  creature  with- 
out legs  and  with  a  very  extensile  anterior  portion 
of  the  body,  begins  feeding  at  once  on  the  specimen 
nearest  at  hand.  This  feeding  is  interesting,  for  the 
larva  fixes  the  little  hooks  that  serve  it  as  jaws  into 
the  body  of  the  louse,  lifts  it  high  in  the  air,  and  holds 
it  thus  helpless,  until  the  juices  have  been  completely 
extracted.  As  each  of  these  slugs  feeds  almost  con- 
tinuously from  ten  days  to  three  weeks,  it  gains  grad- 


THEIR  RELATION  TO  EACH  OTHER      113 

ually  even  on  the  plant  lice  surrounding  it,  and  not  only 
checks  increase  but  lessens  infestation.  Not  all  the 
Syrphid  flies  are  carnivorous,  however;  quite  a  num- 
ber are  scavengers,  some  are  pollen  feeders  and  others 
live  in  the  tissues  of  succulent  leaves  or  stems. 

The  really  important  parasitic  group  is  found  among 
the  Tachinid  flies  and  their  close  allies  resembling 
house-flies,  blow-flies,  flesh-flies  and  others  of  that 
character.  Some  of  them — the  majority  indeed — are 
inconspicuous  grayish  flies  of  moderate  size;  others  are 
metallic  blue  or 
green,  with  or  with- 
out stripes,  more  or 


FIG.  54. — Syrphus 

larva     eating     plant          FIG.  55. — A  Tachinid  fly:  its  eggs  on  body  of 
louse.  caterpillar,  larva  and  pupa. 


less  spiny,  while  a  few  are  large,  set  with  long  bristles 
and  marked  with  contrasting  colors,  appearing  formi- 
dable and  dangerous,  even  if  they  are  not  actually  so. 

These  flies  lay  their  eggs  on  a  variety  of  insects, 
but  more  frequently  on  caterpillars,  and  may  be  said 
to  be  specific  checks  to  a  great  variety  of  cut- worms, 
including  the  army-worm.  The  eggs  are  often  laid  on 
the  outside  of  the  caterpillars  just  back  of  the  head 
where  the  insect  cannot  reach  them,  and  as  they  are 
white  and  of  good  size,  they  are  easily  seen.  These 
Tachinids  come  nearer  to  being  able  to  keep  up  with 
the  increase  of  their  hosts  than  almost  any  other  forms 
that  I  know,  and  I  have  on  several  occasions  seen  army- 
8 


ii4  INSECTS 

worms  on  the  march,  almost  every  one  of  them  with 
the  seeds  of  death  conspicuously  placed  upon  them. 
Out  of  hundreds  of  pupae  gathered  where  armies  had 
been  feeding,  only  single  examples  of  moths  were  ob- 
tained. 

And  in  this  connection  we  might  note  that  a  check 
to  the  further  increase  of  any  plant-feeding  species 
does  not  necessarily  mean  an  immediate  cessation  of 
injury.  Indeed  in  the  armies  of  parasitized  caterpillars, 
every  one  fed  until  it  was  fully  grown,  and  so  far  as 
injury  to  the  crop  was  concerned,  it  made  not  an  ounce 
of  difference  to  the  owner  of  the  grain.  And  so  we 
must  realize  clearly  that  all  these  natural  checks  are 
not  imposed  to  prevent  the  plant-feeding  insects  from 
injuring  the  farmer's  crop,  but  simply  to  prevent  undue 
increase  in  relation  to  the  surroundings  and  to  preserve 
the  balance  of  nature. 

Yet  these  Tachinid  flies  are  among  the  most  effec- 
tive engines  of  destruction  to  the  species  which  they 
infest.  They  develop  quickly,  the  females  lay  a  large 
number  of  eggs  and  they  are  themselves  not  seriously 
affected  by  secondary  parasites.  They  are  therefore 
able  to  maintain  their  relative  proportion  to  their  host 
no  matter  how  rapidly  that  multiplies  because  of  the 
removal  of  other  checks. 

Not  all  Tachinids  lay  their  eggs  directly  on  the 
body  of  the  host.  It  has  recently  been  demonstrated 
by  a  series  of  most  interesting  observations  made  in 
the  course  of  the  gypsy  moth  work  in  Massachusetts, 
that  some  species  lay  very  small  eggs  on  the  leaves  of 
infested  trees  and  that  these  eggs,  eaten  by  the  cater- 
pillar with  the  leaf  tissue,  hatch  when  they  get  into 
the  stomach  and  bore  through  the  walls  into  the  body 
cavity.  Yet  other  forms  lay  their  eggs  on  leaves,  on 
which  caterpillars  are  feeding,  fastening  each  to  the 


THEIR  RELATION  TO  EACH  OTHER      115 

surface  by  a  little  capsule  which  serves  to  hold  the 
active  young  larva  that  hatches  almost  as  soon  as  the 
egg  is  laid.  Sooner  or  later  the  feeding  caterpillar 
comes  within  range  of  this  waiting  maggot  and  then 
with  a  dart  the  parasite  hooks  into  the  skin  of  its  host, 
is  torn  from  the  capsule  attached  to  the  leaf  and  bores 
its  way  in.  It  will  be  readily  appreciated  that  this 
plan  of  scattering  the  numerous  minute  eggs  over  the 
foliage  on  which  caterpillars  are  feeding  is  likely  to 
reach  the  hosts  in  proportion  to  their  abundance. 
If,  for  instance,  a  brood  of  gypsies  completely  strips 
a  tree,  every  Tachinid  egg  on  it  will  also  get  into  the 
caterpillar  stomachs  to  the  undoing  of  a  vast  percentage 
of  them.  It  seems  like  a  hap-hazard  way  of  doing 
things  and,  no  doubt,  when  caterpillars  are  scarce, 
very  few  of  the  thousands  of  Tachinid  eggs  ever  find 
their  way  into  any  appropriate  host. 

It  is  in  the  order  Hymenoptera,  including  the  bees, 
wasps,  ants  and  the  like,  that  we  find  the  most  inter- 
esting specializations  in  the  way  of  predaceous  and 
parasitic  habits;  specializations  so  numerous  and 
interesting  that  they  demand  volumes  for  their  proper 
presentation  and  can  be  only  referred  to  here. 

First  of  all,  there  is  that  enormous  series  of  solitary 
wasps,  including  the  mud- wasps,  digger-wasps,  wood- 
wasps  and  whatever  other  modifications  of  the  term 
may  be  employed;  all  of  which  make  cells  of  some 
kind  either  in  the  ground,  in  pithy  stalks,  against  an 
angle,  in  a  crevice  or  even  attached  to  a  twig,  and  these 
cells  are  stored  with  food  enough  to  bring  the  larva  to 
maturity.  Most  of  the  wasp  larvae  are  helpless,  foot- 
less creatures,  absolutely  incapable  of  seeking  their 
own  food,  and  they  depend  altogether  upon  the  store 
that  has  been  gathered  by  the  parent,  and  that  store 
consists  largely  of  insects  or  spiders,  which  are  par- 


n6 


INSECTS 


alyzed  by  stinging  the  nerve-centres  and  then  retain 
life  enough  to  remain  without  decaying  until  the  wasp 
larva  has  reached  maturity.  One  of  the  commonest 
examples  of  this  sort  is  seen  in  the  shapeless  cell  made 
by  our  blue  mud- wasps  under  porches,  between  the 
slats  of  shutters,  under  the  eaves  or  even  in  garrets. 
If  we  open  one  of  these  cells  in  summer  we  find  it  stored 
with  small  motionless  caterpillars  or  spiders,  and  either 
an  egg  or  an  actively  feeding  wasp  larva  among  them. 


FIG.  56. — A  potter- wasp,  Eumenes  fraterna,  at  a,  its  cell  b  broken  open  at  c,  to 
show  stored  caterpillars. 


On  the  same  order,  but  much  more  neatly  built,  are 
the  mud  cells  of  the  potter-wasps,  which  we  find  fre- 
quently attached  to  low  bushes.  These  are  usually 
filled  with  small  caterpillars,  all  very  much  of  a  size, 
and  so  closely  packed  as  to  fill  the  cell  completely. 
As  every  one  of  these  cells  requires  from  ten  to  twenty 
larvae  to  fill  it  and  a  single  wasp  makes  a  dozen  or  more 
cells,  the  number  of  specimens  thus  used  up  becomes 
quite  a  factor.  Not  all  wasps  feed  on  caterpillars;  in- 
deed, there  is  scarcely  an  order  that  is  not  fed  upon. 
Some  digger-wasps  fill  their  cells  with  grasshoppers; 
others,  that  make  their  cells  in  the  hollow  shoots  of 


THEIR  RELATION  TO  EACH  OTHER      117 

pithy  plants,  collect  plant  lice,  the  larvae  of  small  beetles, 
flies,  or  even  other  Hymenoptera.  There  is  hardly  a 
species  so  small  as  not  to  be  attractive  to  some  of  the 
smaller  wasps,  and  on  the  other  hand,  the  largest  Cicada 
or  tarantula  is  not  safe  from  these  formidable  enemies. 
When  large  species  are  fed  upon,  a  single  specimen 
often  serves  to  bring  a  larva  to  maturity.  The  "taran- 


FIG.  57. — Sphecius  speciosus  carrying  a  cicada  to  its  home. 

tula  hawk,"  when  it  has  succeeded  in  finding  a  suitable 
spider,  and  has  succeeded  in  quieting  it  with  the  formi- 
dable sting,  buries  its  prey  and  lays  a  single  egg  on  it. 
We  have  quite  a  number  of  wasps  that  do  little  more 
than  bury  their  host  and  lay  an  egg  on  it.  The  hand- 
some large  Sphecius  that  preys  on  the  Cicadas  or  dog- 
day  harvest-flies,  makes  a  burrow  with  several  laterals, 
in  each  of  which  it  stores  a  specimen  or  two  which 
serve  to  bring  to  maturity  one  of  the  wasp  larvae. 
There  is  an  exotic  species  living  on  one  of  the  large 
roaches,  which,  after  stinging  its  prey  so  as  to  deprive 


n8  INSECTS 

it  of  voluntary  motion,  is  said  to  seize  it  by  an  antenna 
and  lead  it  into  a  sheltered  spot  before  it  deposits  the 
egg.  The  roach  simply  stays  where  it  was  led  until 
the  wasp  larva  kills  it  by  feeding. 

This  method  of  stupefying  prey  is  a  very  high 
specialization  and  the  stinging  is  by  no  means  a  hap- 
hazard one.  The  wasp  seeks  the  thoracic  ganglion  of 
the  nervous  system  of  adult  insects,  and  may  sting 
several  ganglia  in  caterpillars,  to  make  them  entirely 
quiet.  The  poison  introduced  is  said  to  resemble  formic 
acid  in  composition  and  to  act  as  a  preservative  as  well 
as  a  paralyzing  agent.  But  this  preservative  effect 
has  been  disputed  and  there  are  yet  many  interesting 
points  to  be  elucidated  in  the  biology  of  these  predatory 
wasps.  The  number  of  specimens  collected  and  stored 
by  them  is  very  little  appreciated,  but  it  is  enormous, 
and  the  reduction  in  the  number  of  specimens  thus 
preyed  upon  forms  a  very  important  factor  in  the 
check  to  undue  increase. 

The  social  or  paper-making  wasps  are  also  feeders 
upon  insects;  but  not  so  exclusively,  and  they  make 
no  store  of  food  for  their  larvae.  They  feed  the  young 
from  day  to  day  with  prepared  food,  chewed  into  proper 
condition  by  the  nurses,  and  consisting  partly  of  insect 
fragments  and  partly  of  plant  juices. 

Ants  destroy  many  insects,  but  do  not  usually 
make  specific  war  upon  any  one  species.  They  are 
very  apt  to  attack,  kill  and  eat  almost  any  sort  of 
helpless  creature  that  they  find,  but  few  of  the  species 
of  the  temperate  zone  feed  largely  enough  upon  insect 
food  to  form  a  notable  check  to  any  species. 

Several  families  are  exclusively  or  almost  exclu- 
sively parasitic,  and  these  range  in  size  from  forms 
so  small  as  to  be  scarcely  visible  to  the  untrained  eye, 
to  specimens  expanding  two  inches  or  more,  with  ovi- 


THEIR  RELATION  TO  EACH  OTHER      119 

positors  four  or  five  inches  long.  Very  often,  especially 
among  the  smaller  species,  the  colors  are  brilliantly 
metallic,  and  they  range  all  the  way  from  smoothly 
shining  to  deeply  pitted  as  to  surface. 

There  is  no  species  so  small  and  none  so  well  con- 
cealed in  feeding  as  to  save  it  from  parasites,  and 
these  latter  may  infest  any  stage  from  the  egg  to  the 
adult.  It  is  not  unusual  to  find  a  batch  of  "bug" 
(Hemipterous)  eggs  and  to  hatch  from  them  a  brood  of 
minute  wasps  instead  of  the  little  bugs  that  were  ex- 
pected. And  when  a  lot  of  pupae  or  chrysalids  have 


FIG. 58. — Aphelinus,  parasite  on  armored  scales. 

been  collected,  the  result  may  be  butterflies  or  moths, 
but  is  just  as  likely  to  be  several  hundred  or  only  a 
few  parasites  instead.  The  size  of  the  chrysalis  is 
no  indication  of  the  number  of  parasites  to  be  expected. 
Out  of  a  large  Papilio  or  swallow-tail  we  may  get  a 
single  large  Trogus  and  out  of  a  small  Pieris  or  cabbage 
butterfly  we  may  get  one  hundred  or  more  little  bronze 
Chalcids.  On  a  twig  infested  by  scales  one  may  often 
see  a  large  percentage  with  little  round  holes  through 
the  shell — proof  positive  that  from  each  a  minute 
little  wasp  has  issued;  and  on  a.  leaf  infested  by  plant 
lice,  we  often  see  some  that  are  abnormally  swollen  or 
rounded  and  tending  to  turn  gray.  These  also  are 
parasitized  and  will  shortly  show  a  nice  little  round 


120  INSECTS 

hole  through  an  empty  skin  as  a  reminder  of  the  tragedy. 
Such  parasites  not  only  kill  the  individual,  but  at  once 
stop  all  reproduction,  so  that  every  infested  louse  is 
at  once  eliminated  as  a  factor  in  the  increase  of  the 
species. 

There  are  several  families  of  these  parasitic  wasp- 
lets;  there  is  an  enormous  number  of  species,  often  of 
the  most  bizarre  type  of  structure  and  with  extreme 
diversity  in  habits.  Some  species  remain  within  the 
body  of  their  host  until  they  emerge  as  adults,  often 
giving  no  indication  of  infestation;  others,  when  fully 
grown,  bore  out  through  the  skin  and  form  little  white 

cocoons  on  the  surface.  Some 
of  the  large  Sphinx  caterpillars 
or  horn-worms  are  often  cov- 
ered with  so  many  of  these 
FIG.  59- — Sphinx  caterpillar  little  cocoons  as  to  make  them 

covered  with  cocoons  of  para-  .  ,  . 

sites.  conspicuous  objects.  And 

not  infrequently  the  farmer  or 

gardener  carefully  destroys  these  particular  specimens, 
because,  in  his  opinion,  they  are  covered  with  eggs — 
forgetting  the  fact  that  a  caterpillar  is  incapable  of  re- 
production until  it  has  first  become  a  butterfly  or  moth. 

A  few  species,  usually  those  feeding  on  borers,  are 
external  feeders,  the  parasitic  larva  clinging  to  the 
outside  of  its  host  and  sucking  its  juices  through  a 
small  opening  in  the  skin. 

Some  parasites  proclaim  their  character  by  an  ex- 
ternal protruding  ovipositor  or  egg-laying  tube,  while 
others  have  it  modified  into  a  sting-like  organ.  The 
sting  throughout  the  Hymenoptera  is  nothing  more 
than  a  modified  ovipositor,  and  that  explains  why 
only  females  of  bees,  wasps,  ants,  etc.,  have  it.  When 
the  ovipositor  is  external  and  extended,  it  varies  greatly 
in  length.  Sometimes  it  is  short  and  rigid,  almost 


THEIR  RELATION  TO  EACH  OTHER      121 

like  a  little  borer,  at  others  it  is  long,  slender  and  flex- 
ible, like  a  hair  or  bristle.  Many  of  these  elongated 
types  are  found  among  species  that  attack  boring 
insects  and  some  are  quite  capable  of  piercing  deeply 
into  woody  tissues.  Excellent  examples  of  this  type 
are  found  in  the  species  of  Thalessa,  which  expand 
nearly  two  inches  and  have  ovipositors  almost  or  quite 
four  inches  in  length.  These  are  parasitic  on  boring 


«      S  - 

FIG.  60. — Pimpla  conquisitor;  a  common  parasite,  with  its  larva  and  pupa. 

larvae  of  the  genus  Tremex  which  live  in  burrows  in 
the  trunks  of  maple  and  other  trees.  In  some  way 
these  huge  parasites  seem  able  to  recognize  infested 
trees  and  to  locate,  at  least  approximately,  the  bur- 
rows in  which  the  borers  are  working.  Then  the  long 
ovipositor  comes  into  play,  and  by  a  unique  mechanical 
contrivance  the  slender,  bristle-like  structure  is  forced 
into  the  solid  wood  for  sometimes  its  full  length  before 
the  desired  burrow  is  reached  and  an  egg  can  be  de- 
posited. It  would  be  asking  too  much  that  the  ovi- 
positor should  hit  the  exact  point  where  the  borer 


122  INSECTS 

happens  to  be  at  the  time,  and  when  the  parasitic  egg 
is  once  in  the  gallery,  the  mother  insect  has  done  her 
work.  The  young  'larva  that  hatches  in  the  burrow 
makes  its  way  along  until  it  finds  its  prey,  attaches 
itself,  and  calmly  enjoys  life  at  the  expense  of  its  host. 
But  the  mother  insect  is  by  no  means  infallible,  and 
sometimes  her  ovipositor  fails  to  hit  a  boring,  either 
because  it  is  too  deeply  located  or  because  it  has  been 
missed  by  bad  judgment;  then  nothing  remains  but 
to  try  over  again.  Sometimes,  in  a  vigorously  growing 
tree,  the  sappy  wood  grips  the  ovipositor  and  holds  so 
tightly  that  it  cannot  be  moved  one  way  or  the  other. 
Every  one  who  has  ever  tried  sawing  through  a  green 
log'  knows  what  sort  of  grip  such  wood  may  have,  and 
the  unfortunate  Thalessa  that  is  caught  in  that  way 
is  doomed — usually  to  be  picked  off  by  some  inquisitive 
bird,  sometimes  to  die  of  over-exertion.  I  have  several 
times  tried  to  draw  out  ovipositors  caught  in  that  way 
and  have  never  succeeded:  the  ovipositor  always 
broke  under  the  strain  put  upon  it. 

Maturing  as  quickly  as  many  of  them  do,  they  are 
able,  as  a  rule,  to  keep  up  with  any  unusual  increase 
of  their  host,  and  to  enable  them  to  do  this  even  more 
effectively,  some  species  have  developed  the  remark- 
able ability  of  producing  a  large  number  of  specimens 
from  one  egg — polyembryony,  as  it  is  called.  One  of 
these  minute  species  finds,  for  instance,  a  butterfly  egg, 
and  in  that  lays  its  own  egg,  so  minute  in  size  as  not 
to  interfere  with  the  normal  development  of  the  cater- 
pillar which  hatches  in  due  time,  but  with  that  parasite 
egg  within  its  body.  The  caterpillar  grows  and  so  does 
the  parasite;  but  instead  of  forming  a  larva  and  grow- 
ing normally,  this  parasitic  egg  forms  a  structure  which 
divides  and  subdivides  and  gives  off  segments  almost 
like  those  of  a  tape-worm.  Each  of  these  segments 


THEIR  RELATION  TO  EACH  OTHER      123 


forms  a  larva  which  develops  as  the  host  develops 
and  finally,  when  the  latter  is  full  grown,  it  is  filled 
with  minute,  maggot-like  grubs  ready  to  form  pupa 
cases  which  will  fill  the  caterpillar  skin  so  completely 
that  it  seems  ready  to  burst.  From  a  single  parasite 
egg,  we  may  thus  get  fifty 
or  more  adults;  but  they 
will  all  be  of  one  sex  as 
determined  by  the  egg 
originally  laid.  It  will  be 
readily  seen  what  enor- 
mous reproductive  powers 
some  of  these  minute  spec- 
imens really  have,  for  even 
if  each  laid  only  ten  eggs 
and  each  egg  produced 
fifty  adults,  the  progeny 
would  still  number  500: 
not  at  all  bad  for  such 
small  creatures! 

With  such  enormous 
powers  of  reproduction,  it 
seems  surprising  that  the 
hosts  are  not  completely 
exterminated;  and  yet  as 
we  know,  they  are  not. 
If  we  collect  chrysalids  of 

cabbage  butterflies  in  spring,  the  chances  are  that  out 
of  one  hundred  we  may  get  ten  butterflies  and  several 
thousand  parasites;  more  than  enough  it  would  seem  to 
overpower  the  next  brood  of  caterpillars  completely. 
But  now,  if  we  collect  full-grown  caterpillars  from  the 
scant  lot  produced  by  the  few  spring  butterflies,  we  are 
likely  to  get  a  butterfly  from  every  caterpillar.  From 
the  second  brood  we  are  likely  to  get  almost  as  clean  a 


FIG.  61. — a,  Listomastix  parasite 
laying  a  single  egg  in  the  egg  of  a  moth ; 
b,  the  full-grown  caterpillar  with  par- 
asitic cocoons  from  the  single  egg. 
After  Marchal. 


124  INSECTS 

record,  and  then  butterflies  become  so  plentiful  that  the 
last  brood  of  caterpillars  plays  havoc  in  our  cabbage 
fields.  By  this  time  the  parasites  are  in  evidence  again, 
and  the  hibernating  chrysalids  are  as  badly  infested  as 
they  were  the  year  before.  The  parasite  has  accom- 
plished its  full  purpose,  the  butterflies  are  not  conspicu- 
ously more  abundant  than  they  were  the  spring  before; 
but  throughout  the  summer  the  farmer's  cabbage  has 
paid  the  bill  imposed  by  nature's  methods. 

There  is  yet  another  factor  in  this  connection, 
and  that  is  the  matter  of  what  is  known  as  hyper- 
parasitism,  i.e.,  a  parasite  on  a  parasite.  Not  only  do 
these  parasites  infest  predatory  forms  in  other  orders, 
as  for  instance  the  larvae  and  even  adult  ladybird 
beetles,  but  they  infest  primary  parasites  among  the 
Diptera  and  in  the  Hymenoptera,  very  materially  re- 
ducing their  effectiveness  as  checks  from  the  human 
standpoint,  but  serving  an  important  part  in  preserving 
nature's  balance  and  preventing  the  extermination  of 
the  primary  host.  The  terrific  extent  of  this  secondary 
parasitism  can  best  be  illustrated  by  recording  a 
personal  experience.  I  sorted  out  of  a  collection  of 
cocoons  of  the  Cecropia  moth  295  specimens  that 
were  obviously  parasitized.  Of  these  seventy -six 
specimens  were  infested  by  Ophion  containing  only  a 
single  example  to  each  cocoon ;  the  others  con- 
tained species  of  Spilochalcis  and  Spilocryptus,  each 
cocoon  with  a  mass  of  at  least  twenty  examples.  Out 
of  these  I  bred  nineteen  specimens  of  Ophion,  the 
others  dying  of  disease,  fifty-one  specimens  of  Spilo- 
chalcis and  126  specimens  of  Spilocryptus:  but  in  ad- 
dition I  also  bred  nearly  50,000  specimens  of  Dibrachis, 
a  secondary  parasite  upon  the  two  primaries!  And  the 
matter  goes  even  further:  for  besides  secondary  par- 
asites we  may  have  others  infesting  these,  or  tertiary 


THEIR  RELATION  TO  EACH  OTHER      125 

parasites,  checking  in  turn  too  great  a  reduction  among 
the  primaries. 

It  is  a  merry  war  in  which  all  these  organisms  are 
engaged,  each  one  aiming  only  at  food  for  itself  and 
its  progeny,  and  yet  each  playing  its  part  in  that  game 
of  life  in  which  man  seems  to  be  the  only  one  capable 
of  appreciating  the  conditions,  though  he  is  himself 
involved  and  a  sufferer  as  well  as  a  factor  in  the  game. 

It  is  a  pleasure  to  be  able  to  say  that  the  relation 
of  active  hostility  is  not  the  only  one  existing  between 
insects.  Between  some  there  is  at  least  toleration; 
as  between  others  an  active  friendship  based  on  mutual 
advantage;  in  a  few  cases  there  is  almost  absolute 
dependence. 

The  first  case  of  this  kind  that  comes  to  mind  is  the 
relation  of  certain  ants  to  certain  plant  lice,  and  assuredly 
we  have  nothing  in  the  range  of  insect  behavior  that 
exceeds  in  interest  this  cultivation  or  fostering  of  a 
creature  so  far  different,  until  we  get  it  in  the  relation 
of  the  human  being  to  his  domestic  animals.  The 
relation  is  even  closer,  because  so  much  has  the  lapse 
of  time  acted  upon  this  interdependence  that,  while 
the  elimination  of  the  plant  louse  might  make  little 
difference  to  the  ant,  the  elimination  of  the  ant  would, 
in  many  cases,  mean  the  destruction  of  the  plant  louse. 

It  is  not  possible  in  this  connection  to  do  more  than 
mention  the  fact  that  among  the  social  insects  there 
are  a  number  of  different  castes  and  forms,  each  of  which 
has  its  own  function  in  the  community.  That  is  a  mat- 
ter of  internal  administration  and  is  regulated  by  each 
species  in  accordance  with  the  conditions  which  have 
been  developed  by  the  stress  of  the  surroundings.  It 
is  a  little  different  when  the  matter  of  slavery  comes 
to  be  considered;  when  we  find  that  certain  species 
of  ants  actually  make  war  upon  weaker  forms  to  obtain 


126  INSECTS 

servants  to  do  their  work;  and  yet  even  this  is  a  matter 
of  domestic  economy  to  be  covered  rather  by  a 
student  who,  like  Dr.  William  Morton  Wheeler,  has 
•studied  the  ants  in  their  relation  to  each  other,  than 
by  a  general  work,  dealing  rather  with  the  relations 
of  different  kinds  of  insects. 

In  the  domestic  economy  of  ants,  we  have  to  con- 
sider those  species  which  are  of  use  to  the  ants  them- 
selves and  are  fostered  and  cultivated  for  that  reason, 
and  those  that  maintain  themselves  in  the  nests  in 
spite  of  opposition  or  by  toleration  only.  The  first 
series  are  those  from  which  the  ants  derive  a  direct 
benefit;  the  others  are  those  which  do  them  no  direct 
harm  and  rather  indirectly  benefit  them. 

Perhaps  plant  lice  are  the  best  known  of  those 
that  are  directly  fostered,  and  they  are  favored  because 
of  the  saccharine  secretion  or  "honey"  which  they 
produce.  The  simplest  form  of  this  relation  is  where  ants 
visit  colonies  of  plant  lice  on  vegetation  and,  by  stim- 
ulating or  irritating  the  specimens  with  their  antennae, 
induce  them  to  eject  a  drop  of  the  sweet  secretion  which 
is  then  gathered  up.  In  return  the  ants  attack  and 
drive  off  a  great  many  enemies  that  would  otherwise 
destroy  their  herds.  The  next  stage  is  when  ants 
build  galleries  around  roots  infested  by  plant  lice  and 
directly  favor  them  by  freeing  from  soil  and  other  in- 
cumbrances  an  abundance  of  feeding  surface.  This 
would  seem  to  give  the  plant  lice  a  free  field  for  increase ; 
but  not  only  do  parasites  find  their  way  into  the  nests 
but  even  larvae  of  ladybird  beetles  occur  in  consider- 
able numbers.  These  latter,  however,  in  almost  every 
case,  produce  from  specialized  glandular  structures, 
waxy  fibres  which  seem  almost  or  quite  as  attractive 
to  the  ants  as  the  secretions  of  the  plant  lice.  They 
therefore  feed  upon  these  processes  or  rather  excre- 


THEIR  RELATION  TO  EACH  OTHER      127 

tions,  and  appear  to  forgive  the  intruders  their  tres- 
passes against  the  Aphids.  A  still  further  special- 
ization, decidedly  more  important  from  the  economic 
standpoint,  is  found  among  those  ants  that  gather  and 
preserve  the  eggs  of  plant  lice  during  the  fall  and  winter, 
and  colonize  them  on  suitable  food  plants  in  the  spring. 
The  strawberry  louse  and  corn-root  louse  are  examples 
of  this  kind,  and  both  of  these  Aphids  would  find  it 
difficult  if  not  impossible  to  maintain  themselves  were 
it  not  for  the  assistance  given  by  the  ants.  The  economic 
importance  of  the  matter  comes  in  when  we  consider 
that,  except  for  the  ants,  it  would  be  easy  to  starve 
out  the  Aphids  by  a  mere  rotation  of  crops.  In  some 
instances,  where  the  plant  lice  will  not  live  under- 
ground, the  ants  build  protecting  shelters  around  the 
colonies  on  their  food  plants,  and  thus  gain  all  the 
advantages  that  other  species  get  from  their  under- 
ground forms. 

Indirectly,  therefore,  ants  may  become  decidedly 
injurious  to  a  growing  crop,  even  though  they  do 
not  themselves  feed  upon  it,  and  the  best  way  of 
dealing  with  an  injurious  form  may  be  through  its 
protecting  ant. 

Besides  plant  lice,  scales  are  often  visited  and  here 
again  the  protection  accorded  by  ants  in  the  destruc- 
tion of  forms  inimical  to  the  scales  is  the  return  ren- 
dered for  the  food  supply.  It  has  been  charged,  indeed, 
that  the  Scutellista  introduced  into  California  to  con- 
trol the  black  scale,  has  been  practically  destroyed  by 
ants  that  obtain  honey-dew  from  the  scales.  Scales, 
however,  are  never  really  domesticated  like  plant  lice, 
and  while  they  are  of  very  great  importance  to  some 
ants  they  are  never  entirely  dependent  upon  them  for 
existence.  Some  few  species  among  the  tree-hoppers 
and  frog- hoppers,  also  excreting  honey-dew  or  waxy 


128 


INSECTS 


matter,  are  found  in  the  nests  or  galleries  of  ants,  and 
are  at  least  tolerated  if  not  directly  favored. 

Then,  as  in  all  great  cities,  so  the  large  formicaries 
are  inhabited  by  a  rabble  of  scavengers,  thieves,  mess- 
mates of  all  kinds,  living  in  friendly  or  hostile  relations 
as  the  case  may  be.  These  are  of  the  most  diverse 
characters,  from  the  lowly  Thysanuran  to  the  fellow 
ant  of  smaller  size  or  dominating  type.  Over  1000 
species  of  Myrmecophiles,  as  such  species  are  called, 

have  been  already  listed 
and  their  habits  more  or 
less  fully  studied  and  there 
is  no  doubt  that  there  are 
at  least  as  many  more. 
Some  of  these,  like  a  va- 
riety of  rove-beetles  and 
some  other  of  the  Clavi- 
corn  series,  are  scavengers, 
living  on  the  decaying  par- 
ticles of  organic  matter 
found  in  the  galleries,  and 
may  repay  the  ants  by  ex- 
cretory substances  coming 

from  specialized  tufts  of  hair  or  glandular  surfaces. 
These  are  favored  and  protected,  while  others  that  pay 
nothing  for  their  living  usually  keep  out  of  the  way  as 
much  as  possible.  Some  few  species,  belonging  to  the 
Histeridcz  or  pill  beetles,  are  positively  harmful  to  the 
colonies,  but  are  so  well  protected  by  their  shining  armor 
of  chitin,  that  the  ants  can  do  nothing  with  them.  It  is 
a  case  of  simply  enduring  what  cannot  be  cured,  and 
such  intruders  must  be  constantly  on  their  guard  not 
to  expose  leg  or  antenna  w^hen  the  owners  of  the  nest 
are  about.  A  few  caterpillars  have  been  found  in  for- 
micaries and  these  feed  on  the  dead  leaves  in,  over,  or 


FIG.   62. — Hister    species    found    in 
ants'  nests. 


THEIR  RELATION  TO  EACH  OTHER      I2Q 

about  the  nests.  The  ants  seem  to  pay  little  attention 
to  any  save  a  few  Lycaenid  larvae  that  have  glandular 
structures  producing  attractive  secretions.  A  few 
species  of  small  crickets  and  other  Orthoptera  help  to 
swell  the  list  of  guests,  and  several  fly  larvae  occur. 
Some  of  these  inhabitants  steal  the  supplies  gathered 
by  the  owners  of  the  nest,  and  against  these  relentless 
war  is  waged  whenever  the  ants  recognize  them;  but 
there  are  curiosities  in  ant  intelligence  which,  in 
some  cases,  seems  to  amount  to  downright  stupidity, 
and  which  prevents  them  from  recognizing  the  thieves 
in  the  most  vulnerable  stage.  Perhaps  the  worst 
thieves  in  the  formicaries  of  large  species  are  other, 
much  smaller  ants  that  run  their  narrow  galleries  so 
as  to  tap  the  larger  tunnels,  and  when  they  are  de- 
tected stealing  disappear  into  their  own  streets  into 
which  the  larger  form  cannot  follow.  There  are  also 
direct  parasites  adapted  to  live  in  such  communities 
without  recognition,  but  only  mere  mention  can  be 
made  of  these.  There  is  a  good  deal  of  human  nature 
in  an  ant  city  and  the  history  of  what  takes  place  in 
such  a  city  has  been  written  most  accurately  and  en- 
tertainingly by  Dr.  Wheeler,  who  is  on  terms  of  most 
intimate  acquaintance  with  these  species. 


CHAPTER  V. 

THEIR  RELATION  TO  THE  ANIMALS  THAT 
FEED  ON  THEM 

THIS  subject  might  be  dismissed  with  a  very  few 
words  in  the  statement  that  a  large  number  of  birds  sub- 
sists entirely  on  insect  food,  another  large  number  feeds 
on  insects  during  certain  seasons  or  takes  them  indiffer- 
ently as  part  of  the  general  diet,  and  that  the  same  is 
true  of  certain  mammals,  reptiles,  batrachians  and  the 
like.  Active  defence  very  few  insects  are  able  to  make 
against  any  of  these  enemies,  and  we  may  say  broadly 
that  the  number  of  insects  that  may  be  destroyed  by  ver- 
tebrate enemies  is  limited  only  by  their  appetite  and 
their  ability  to  find  prey.  The  only  practical  defences 
that  an  insect  has,  are  its  ability  to  escape  the  notice  of 
its  pursuer  and  its  enormous  fecundity ;  points  that  have 
been  elucidated  to  some  extent  in  a  previous  chapter. 

So  we  can  say,  roughly,  that  all  kinds  of  insects 
serve  as  food  for  some  kind  of  animal.  That  is  not 
strictly  true,  of  course,  for  there  are  some  that  are  so 
minute  that  they  are  taken  only  by  accident  and  a  few 
others  that  seem  to  be  so  offensive  that  no  animal  will 
touch  them;  but  as  a  general  statement  it  is  accurate 
enough.  Some  birds  and  animals  eat  indifferently 
any  thing  that  comes  along;  others  have  a  very  limited 
diet  and  go  outside  of  their  normal  range  only  under 
the  pressure  of  necessity,  which  is  usually  spelled 
hunger.  Some  animals  eat  what  others  avoid,  e.g., 
hairy  caterpillars,  and  some  insects  feed  so  as  to  be  out 
of  reach  of  all  save  animals  especially  adapted  to  find 
them,  e.g.,  borers  sought  by  woodpeckers. 

130 


THEIR  RELATION  TO  ANIMALS  131 

Among  animal  feeders  on  insects  we  may  enu- 
merate toads,  frogs,  snakes,  lizards  and  all  their  rela- 
tives; the  tortoises  generally;  rats  and  mice  and  their 
allies;  the  shrews  and  their  allies ;  bats,  coons,  opossums, 
moles  and,  to  a  less  extent,  the  larger  carnivora.  The 
smaller  species  of  the  cat  and  dog  tribe  eat  a  large 
number  of  insects  and  even  bears  count  them  among 
their  list  of  eatables.  Fish  eat  the  aquatic  species  when- 
ever they  can  get  at  them,  and  birds  have  been  already 
referred  to.  Now,  when  we  realize  that  the  insecti- 
vores  among  the  mammals  form  a  very  numerous 
and  important  series,  and  that  the  carnivores  assist, 
we  get  at  once  a  formidable  list  of  destroyers  against 
which,  as  already  stated,  the  insects  have  little  defence. 
The  matter  of  protective  resemblance  of  course  comes 
in;  but  that  plays  really  a  very  subordinate  part. 
There  is  no  doubt  that  many  insects  resemble  their 
surroundings  so  closely  that  they  are  with  difficulty 
to  be  seen;  but  they  can  be  seen  by  the  trained  eye. 
Some  species  of  moths  sit  openly  on  the  tree  trunks 
in  city  streets  and  hundreds  of  passers-by  absolutely 
fail  to  see  them;  but  to  the  first  entomologist  that 
comes  along  they  are  as  obvious  as  if  they  had  been 
placed  there  to  attract  his  attention.  It  would  be 
ranking  bird  and  animal  senses  very  low  indeed  if  we 
seriously  believed  that  such  resemblances  made  them 
actually  invisible  to  those  who  have  in  hunger  the 
best  sharpener  for  the  senses  that  can  be  imagined. 
That  such  resemblances  do  protect  from  casual  ma- 
rauders there  is  little  doubt,  and  that  there  is  a  better 
chance  of  escape  from  a  casual  search  than  there  would 
be  were  the  insects  more  conspicuous  we  may  assume; 
but  that  the  resemblance  is  protective  to  the  extent  that 
is  sometimes  claimed  is  at  least  open  to  serious  doubt. 

"Playing    possum"    is    a    much    better    protection, 


132  INSECTS 

and  is  resorted  to  by  many  insects.  This  means  that 
when  they  are  disturbed  and  apprehend  danger,  the 
specimens  draw  in  legs  and  feelers,  permit  themselves 
to  drop  to  the  ground  and  remain  absolutely  quiescent 
until  they  believe  the  danger  past.  This  very  habit, 
however,  delivers  some  of  the  economically  important 
species  into  the  hands  of  their  arch-enemy  man,  who 
spreads  a  sheet  or  other  catcher  beneath  a  tree  or  vine, 
jars  the  infested  plant  and  gathers  in  the  specimens 
which  on  the  white  background  are  conspicuous  enough, 
though  in  sod  or  on  the  bare  earth  they  would  be 
well-nigh  invisible. 

Warning  colors  and  protective  mimicry  are  other 
passive  defenses.  Warning  colors  are  simply  bright 
or  contrasting  tints  that  indicate  a  species  unpalatable 
to  ordinary  animal  feeders  on  insects  of  that  descrip- 
tion. That  there  are  such  species  there  is  no  doubt, 
for  they  seem  almost  entirely  safe  from  predatory  foes. 
Their  dress  expresses  the  legend  "not  good  to  eat" 
and  so  they  are  left  unharmed.  Now  one  type  of  pro- 
tective mimicry  is  found  where  a  species  of  another 
group  or  series  normally  good  to  eat  so  closely  re- 
sembles this  unpalatable  form  as  to  be  readily  mis- 
taken for  it,  and  some  of  these  resemblances  are  ex- 
tremely close.  Another  type  is  when  an  inoffensive 
insect  so  closely  resembles  one  that  is  capable  of  de- 
fence, that  its  enemies  hesitate  to  attack.  The  re- 
semblance of  some  Sesiid  moths  and  Conopid  flies  to 
wasps  is  a  case  in  point.  In  such  instances  it  is  quite 
usual  to  find  that  the  mimic  has  some  of  the  same 
tricks  of  habit  as  the  protected  form  and  this  is  at 
least  as  powerful  a  safeguard  as  the  color  alone. 

Now  what  place  do  these  vertebrate  enemies  hold 
in  the  series  of  checks  to  insect  increase,  and  how  much 
do  they  benefit  man — the  farmer  and  fruit  grower? 


THEIR  RELATION  TO  ANIMALS  133 

We  have  here  two  questions  of  very  great  interest  and 
importance  and  the  answer  to  the  one  does  not  by  any 
means  determine  the  answer  to  the  other.  That  all 
these  birds  and  other  animals  eat  untold  thousands 
of  insects  each  year  is  undoubtedly  true,  and  that  this 
is  an  important  factor  in  limiting  the  number  of  speci- 
mens, is  unquestionable;  but  compared  with  the  num- 
bers destroyed  by  disease,  by  climatic  conditions  and 
by  other  insects,  the  figures  are  really  insignificant. 
It  goes  without  saying  that  these  remarks  are  based 
on  normal,  natural  conditions,  for  it  is  quite  possible 
to  change  the  conclusion  under  control.  For  instance, 
if  I  turn  a  flock  of  guinea-hens  into  a  field  infested 
with  grasshoppers,  the  fate  of  those  hoppers  is  sealed, 
provided  there  are  guineas  enough  to  eat  them.  I 
have  seen  some  fields  of  alfalfa,  however,  in  the  foot- 
hills of  the  Rocky  Mountains,  where  the  grasshoppers 
were  so  numerous  that  all  the  guineas  within  the  county 
would  make  no  serious  impression  on  them. 

As  to  the  food  of  birds  we  are  left  in  little  doubt. 
Many  species  have  been  shot  in  large  numbers  at  all 
seasons  and  have  had  the  stomach  contents  carefully 
determined  and  classified.  One  striking  fact  that 
appears  from  all  the  lists  that  have  been  published,  is 
that  the  large  majority  of  insect  feeders  among  the 
birds  pick  up  anything  they  can  get  hold  of  most  easily, 
and  that  the  commonest  reasonably  palatable  forms 
are  those  most  frequently  taken.  Naturally,  though, 
this  does  not  apply  to  birds  fitted  for  a  special  diet  like 
the  woodpeckers.  Among  the  other  animals  almost 
the  same  conclusion  applies,  again  making  exceptions 
of  such  creatures  as  moles  and  others  which  are  natur- 
ally limited  to  underground  forms  or  to  species  occur- 
ring in  limited  or  specialized  areas. 

One  consequence  of  this  is  that  a  great  many  eco- 


134  INSECTS 

nomically  harmless  insects  furnish  a  large  percentage 
of  the  food:  ants,  flies,  fly  larvae  in  excrement  and 
similar  species.  Another  is,  that  a  great  many  posi- 
tively useful  insects  are  taken ;  less  so  those  of  absolute 
importance  to  man  by  reason  of  their  direct  contri- 
butions than  those  indirect  friends,  the  predatory  and 
parasitic  forms;  and  spiders  may  for  this  purpose  be 
counted  as  useful  insects.  Furthermore  birds  do  not 
discriminate  between  insects  that  are  parasitized  and 
those  that  are  not.  Hence  in  eating  cut- worms  there 
is  at  least  an  even  chance  that  parasitized  forms  are 
taken  as  freely  as  those  not  so  infested.  In  eating  a 
parasitized  specimen  the  only  benefit  derived  by  cut- 
ting short  its  life  is  the  saving  of  its  food  for  a  few  days, 
because  it  could  not  have  come  to  the  reproductive 
stage  anyway;  while  a  positive  harm  has  been  done 
in  cutting  short  the  parasites  which  might  have  de- 
stroyed a  hundred  cut-worms  the  season  following. 
It  is  always  possible  to  draw  a  variety  of  conclusions 
from  a  list  of  insects  found  in  bird  stomachs,  and  that 
generally  drawn,  to  wit,  that  birds  are  always  of  very 
great  importance  to  the  farmer  and  fruit-grower,  is 
usually  no  more  warranted  than  the  contrary  one  that 
birds  are  of  no  use  whatever. 

There  never  yet  was  an  apple  orchard  kept  free 
from  codling  moth  by  birds  no  matter  how  much  chance 
the  birds  had:  in  fact  in  neglected  old  orchards  where 
birds  and  other  animals  are  never  disturbed  it  is  rather 
the  exception  to  find  a  fruit  free  from  insect  attack. 
The  same  is  true  of  the  plum  curculio.  There  never 
yet  was  a  field  of  grain  freed  of  green-fly  by  birds,  nor  a 
tree  of  any  kind  saved  by  them  from  destruction  by  San 
Jose"  scale.  In  many  cases  woodpeckers  do  more  real  in- 
jury to  a  tree  than  the  larva  they  get  out  would  have 
done,  and  the  elm  in  a  grove  where  birds  hold  undisturbed 


THEIR  RELATION  TO  ANIMALS  13$ 

sway  is  just  as  likely  to  be  defoliated  by  the  elm-leaf 
beetle  as  its  fellow  in  the  city  streets  where  the  English 
sparrow  holds  the  fort.  It  is  correct  to  say  that  as 
against  the  common  pests  of  the  farm,  the  field,  the  or- 
chard and  the  garden,  neither  birds  nor  other  vertebrate 
animals  are  of  the  least  practical  benefit  and  that  the 
farmer  and  fruit-grower  would  as  to  them  be  no  worse  off 
if  every  insectivorous  bird  and  other  animal  were  killed. 

And  yet  withal  it  is  not  a  fair  conclusion,  to  con- 
tend that  insectivorous  birds  and  animals  do  no  good. 
They  do,  no  doubt,  constitute  a  very  useful  and  im- 
portant check  to  many  species  that  would  otherwise 
be  much  more  abundant  than  they  are,  and  a  careful 
preservation  of  every  insectivorous  bird  and  animal  is 
good  policy — even  such  forms  as  quail,  partridges  and 
their  allies,  which  are  now  guarded  at  one  season  simply 
that  they  may  be  shot  at  another. 

It  must  again  be  emphasized  that  birds  and  other 
animals  constitute  only  one  of  the  checks  to  insect  in- 
crease and,  as  against  climate,  disease,  parasitic  and 
predatory  insects,  a  very  minor  and  insignificant  one. 
We  must  also  remember  again  that  for  a  naturally 
abundant  species  the  abundance  was  fixed  in  spite 
of  all  the  natural  checks,  including  birds  and  animals. 
Now  when  such  an  abundant  insect  becomes  destruc- 
tive by  reason  of  undue  increase  from  any  cause,  the 
very  last  factor  to  become  important  in  bringing  it 
back  to  normal  conditions  is  the  vertebrate  enemy 
list,  including  birds,  because  their  number  and  ability 
to  consume  remains  practically  a  fixed  quantity  due 
to  their  slow  rate  of  multiplication.  It  sounds  large 
when  we  find  100  larvae  of  an  elm-leaf  beetle  in  a  bird 
stomach  and  find  100  birds  to  an  acre;  but  when  we 
find  100  larvae  on  a  dozen  leaves  and  many  thousands 
of  leaves  on  a  tree,  the  figures  lose  in  impressiveness. 


i36  INSECTS 

It  must  be  realized  that  under  natural  conditions  in- 
sectivorous animals  depend  on  insects  for  their  con- 
tinued existence,  and  that  when  fed  to  the  full,  there 
must  yet  remain  enough  to  supply  food  for  the  season 
to  come  in  spite  of  all  other  natural  checks,  as  other- 
wise the  animals,  birds  and  others,  would  themselves 
starve  to  death.  I  have  already  pointed  out  how  pecu- 
liarly well  some  of  the  parasitic  and  predatory  forms 
are  adapted  to  gain  control  of  a  runaway  species,  and 
it  remains  to  be  added  that  among  the  effective  forms 
that  check  the  undue  increase  of  parasites,  are  the 
birds  and  other  animals  that  eat  parasites  and  par- 
asitized insects. 

Now,  in  spite  of  the  fact  that  I  am  convinced  that 
all  vertebrate  animal  life,  so  far  as  it  affects  the  insects 
that  are  injurious  to  our  farm  crops,  is  of  little  real 
benefit  to  the  farmer  and  fruit-grower,  I  would  not 
for  a  moment  argue  in  favor  of  the  destruction  of  any 
form  of  bird  or  animal  life  not  absolutely  harmful  to 
cultivated  crops.  Birds  have  their  place  in  preserving 
the  balance  of  nature  and  any  interference  with  them 
is  sure  to  react  unfavorably  to  the  agriculturist  by 
increasing  his  troubles  in  some  direction;  and  while 
under  normal  conditions  birds  may  be  of  little  value, 
yet  under  abnormal  conditions  which  tend  to  remove 
checks  of  other  kinds,  any  increase  in  bird  and  similar 
enemies  would  assist  in  replacing  the  other  checks. 

I  would,  therefore,  rigidly  protect  every  insectivorous 
bird  and  other  animal,  including  non- venomous  snakes 
and  toads,  and  I  would  also  protect  every  animal  that 
feeds  upon  insects  at  any  time,  providing  the  direct  in- 
jury done  to  crops  or  other  farm  products  is  not  at  any 
time  sufficient  to  cause  appreciable  loss  to  agriculturists. 

I  would  not  hesitate  advising  the  destruction  of 
robins,  crows,  blackbirds  or  others  when  actually  en- 


THEIR  RELATION  TO  ANIMALS  137 

gaged  in  feeding  on  fruit  or  grain ;  but  I  would  absolute- 
ly prohibit  their  killing  at  any  time  as  a  mere  matter  of 
sport.  I  would  be  in  favor  of  protecting  every  bird  not 
absolutely  harmful ;  but  of  no  protection  whatever  to  any 
animal  merely  for  the  purpose  of  keeping  it  to  be  shot 
at  during  some  specified  period  by  so-called  sportsmen. 

I  have  no  point  of  difference  with  those  who  are 
seeking  the  protection  of  bird  and  other  animal  life. 
I  simply  wish  to  record  my  disagreement  with  some  of 
the  reasons  and  arguments  advanced  by  them,  and  to 
guard  against  an  exaggerated  belief  in  the  value  and 
usefulness  of  our  furred  and  feathered  friends. 

Interference  with  natural  conditions  by  introducing 
new  factors  does  not  always  turn  out  well  and  should 
not  be  resorted  to  without  a  careful  preliminary  study 
of  possible  consequences  from  all  points  of  view.  When 
the  English  sparrow  was  introduced  into  North  America 
only  one  point  was  kept  in  mind:  get  something  that 
will  eat  the  span-worm,  the  larva  of  the  geometrid 
moth,  Ennomos  subsignaria.  The  sparrow  really  did 
accomplish  that  feat;  but  is  now  a  greater  nuisance 
than  the  span-worms  ever  were  and  is  a  direct  pro- 
tector of  certain  species  which  never  occur  in  trouble- 
some numbers  outside  the  region  dominated  by  it. 
The  common  Tussock  or  vaporer  moth  of  the  east  is  an 
excellent  example  of  this,  and  hardly  less  striking  is  the 
case  of  the  wood-leopard  moth  which  has  not  become 
injurious  in  this  country  anywhere  except  in  cities  and 
towns  where  the  sparrows  keep  all  other  birds  out. 

Chickens,  ducks,  geese,  and  especially  turkeys  and 
guinea-fowl  are  great  feeders  on  insect  life  and  may 
sometimes  be  used  practically,  and  the  useful  hog 
esteems  wire- worms,  white  grubs  and  similar  creatures 
as  tid-bits  to  be  eagerly  sought  and  worthy  of  con- 
siderable rooting  for. 


CHAPTER  VI 

THEIR  RELATION  TO  WEATHER  AND  DISEASES 
THAT  AFFECT  THEM 

VERY  few  insects  occur  throughout  the  world,  and 
those  that  do  are  usually  such  as  have  been  distributed 
by  or  have  followed  in  the  track  of  man  or  his  commerce ; 
but  there  is  no  portion  of  our  globe  where  life  occurs 
at  all,  in  which  insects  are  not  found.  In  the  polar 
regions  they  are  often  unpleasantly  conspicuous,  and 
in  the  tropics  they  frequently  render  life  burdensome. 
When  the  arctic  snows  begin  to  melt  during  the  short 
summer  and  form  puddles  on  the  mossy  surface,  mos- 
quito larvae  appear,  and  even  when  there  is  an  ice  coat- 
ing over  the  pools  at  times  they  maintain  themselves 
and  come  to  maturity.  Indeed  some  wrigglers  and  other 
insects  will  stand  freezing  or  imbedding  in  ice,  and  come 
out  none  the  worse  when  a  warmer  temperature  thaws 
them  into  a  liquid  medium.  There  are  insects,  then, 
that  survive  in  one  condition  or  another  the  extremes 
of  arctic  cold:  there  are  others  that  flourish  under  the 
opposite  conditions  of  tropical  heat.  Indeed  the  lux- 
uriant vegetation  of  the  equatorial  regions  is  accom- 
panied by  an  infinite  variety  of  insect  life,  a  variety  so 
great  that  we  have  just  begun  to  appreciate  it,  and 
which  will  give  a  field  for  study  to  entomologists  for 
generations  to  come.  Furthermore,  as  we  have  found 
aquatic  forms  in  water  at  temperatures  low  enough  to 
form  ice,  so  we  find  others  in  waters  whose  temperature 
ranges  close  to  the  boiling  point.  There  are  some 
regions  so  arid  that  neither  vegetable  nor  animal  life 
exists  in  them;  but  if  at  any  time  under  the  influence 

138 


THEIR  RELATION  TO  WEATHER         139 

of  rain,  vegetation  appears  at  all,  insects  will  be  found 
on  it.  And  again,  some  insects  occur  in  midocean 
among  masses  of  seaweed,  undergo  their  transforma- 
tions and  develop  generation  after  generation  without 
ever  coming  within  reach  of  land. 

So  we  find  that  there  is  no  climate  and  almost  no 
earthly  condition  in  or  under  which  insects  do  not 
exist;  yet,  on  the  other  hand,  insects  are,  as  a  rule, 
extremely  sensitive  to  changes  in  climatic  conditions, 
and  some  of  them  succumb  easily  to  any  extreme  range 
of  temperature,  even  within  their  native  home.  Zo- 
ologists have  divided  the  world  into  faunal  regions 
based  on  climate,  and  have  subdivided  these  into 
smaller  regions  based  on  the  geographical  conforma- 
tion of  the  country  whose  fauna  is  under  considera- 
tion; and  we  have  found  in  our  studies  that  a  large 
number  of  insect  species  have  an  extremely  restricted 
faunal  range.  Beyond  that  range  they  do  not  thrive  at 
all,  and  not  infrequently,  where  no  natural  barrier 
seems  to  exist,  spread  nevertheless  does  not  take  place. 
The  check  in  such  cases  is  weather  in  the  broad  sense 
of  that  term,  or,  more  accurately,  the  meteorological 
conditions.  The  mere  fact  that  any  species  of  insect 
is  regionally  distributed  usually  indicates  that  any 
climatic  condition  not  normal  to  such  region  would 
be  fatal  to  it.  An  apparent  exception  occurs  when 
insects  are  confined  to  one  food  plant — the  occurrence 
of  such  plant  being  then  a  condition  precedent  10  its 
existence  at  all.  But  this  is  merely  shifting  factors 
about  a  little,  for  usually  the  climatic  conditions  deter- 
mine the  distribution  of  the  plant  and,  in  consequence, 
really  of  the  insect  as  well. 

We  know  that  occasionally  we  have  abnormal 
seasons,  and  sometimes  several  seasons  of  the  same 
kind  may  occur  in  succession.  When  that  happens 


i4o  INSECTS 

insects  may  begin  a  migration  beyond  tlieir  original 
limits  and  may  extend  a  long  distance  into  adjacent 
territory,  only  to  be  destroyed  when  a  recurrence  of 
normal  weather  conditions  renders  the  invaded  area 
unfit  as  a  place  of  habitation.  An  example  of  that 
character  occurred  in  1896  when  the  Harlequin  cabbage 
bug  invaded  New  Jersey  and  Pennsylvania,  its  normal 
range  not  extending  north  of  Maryland  along  the  At- 
lantic coast.  But  although  it  was  present  in  that  year 
in  destructive  numbers,  it  was  completely  killed  off 
during  the  winter  following  and  has  not  been  found 
in  New  Jersey  since.  It  is  an  example  of  an  insect 
rigorously  restricted  in  distribution  by  climatic  con- 
ditions, although  its  food  plants  are  widely  distributed 
outside  of  its  own  faunal  limitations. 

But  occasionally  matters  do  not  terminate  as  sim- 
ply. It  may  happen  that  an  insect  long  confined  to 
a  definite  faunal  area  may  be  started  on  a  migration 
along  the  line  of  its  food  plant,  and  may  be  found  to 
possess  sufficient  powers  of  adaptation  to  continue  its 
life  under  conditions  varying  materially  from  those  in 
which  it  started.  A  striking  example  of  this  is  found 
in  the  case  of  the  Sphinx  catalpa  which  in  its  caterpillar 
stage  feeds  only  on  Catalpa  and  which,  up  to  a  few 
years  ago,  did  not  range  north  of  Virginia  and  Ken- 
tucky, although  its  food  plant  extends  into  New  York 
and  Pennsylvania.  Somewhere  about  1897  it  began 
to  extend  northward  through  Maryland  and  Delaware 
into  Pennsylvania,  and  year  by  year  it  has  extended 
that  range  until  it  has  reached  the  headwaters  of  the 
Delaware  River,  and  has  extended  throughout  New 
Jersey  into  New  York  State.  And  this  extension  is 
not  of  a  few  individuals  only;  but  of  a  horde,  capable 
of  causing  defoliation  and  serious  injury  to  the  trees 
attacked.  At  present  it  seems  as  if  the  species  had 


THEIR  RELATION  TO  WEATHER          141 

•succeeded  in  establishing  itself  in  a  faunal  region  defi- 
nitely varying  from  that  in  which  it  started;  but  there 
are  indications  also  that  it  has  reached  its  limit. 

A  yet  more  striking  case  is  found  in  the  migration 
of  the  cotton -boll  weevil,  a  species  indigenous  south  of 
the  line  between  Mexico  and  the  United  States,  which 
began  its  invasion  into  our  territory  somewhere  about 
1893  and  has  been  annually  extending  its  range  through 
the  cotton-growing  states  since  that  time.  So  great  a 
variety  of  climatic  conditions  is  now  represented  in 
its  distribution,  that  there  seems  to  be  no  reason  to 
believe  that  its  spread  will  be  checked  until  it  has 
reached  the  faunal  limits  of  its  food  plant;  although 
that  period  may  be  materially  retarded  by  the  quaran- 
tine and  other  regulations  now  adopted  by  the  cotton- 
growing  states. 

These  are  instances  of  natural  spread  from  one 
faunal  region  to  one  adjacent  thereto,  along  the  line 
of  the  food  plant.  There  are  other  cases  where  insects 
have  been  accidentally  introduced  on  trees,  shrubs  or 
plants  from  one  country  to  another,  into  which  it  could 
not  have  spread  naturally  and  where  the  climatic  con- 
ditions in  the  new  home  suited  the  species  so  much  better 
that  injury  became  much  more  severe  as  specimens 
became  more  numerous.  An  example  of  this  character 
is  found  in  the  recent  introduction  of  the  "white-fly" 
of  the  Citrus  from  Florida  to  California,  where  the  dry 
climate  exempts  the  insect  from  certain  disease  and 
other  checks  favored  by  the  more  humid  climate  of  the 
eastern  country. 

Leaving  aside  for  the  moment  cases  where  migra- 
tions have  been  from  south  to  north  when,  under  favor- 
ing conditions  insects  from  mild  temperature  regions 
extended  into  normally  more  rigorous  climates,  it 
sometimes  happens  that  conditions  reverse,  and  in- 


142  INSECTS 

stead  of  a  higher  temperature  extending  northward,' 
a  low  temperature  extends  southward.  This  is  rarely 
followed  or  accompanied  by  a  southward  migration, 
but  is  very  frequently  attended  by  a  great  mortality 
among  the  southern  insects  which  are  unable  to  with- 
stand the  drop  in  temperature.  Some  species,  indeed, 
are  so  sensitive  to  cold  that  a  drop  of  10°  or  even  5° 
below  the  normal  winter  temperature  causes  a  serious 
mortality. 

Besides  temperature,  the  amount  of  moisture  has 
a  very  decided  effect  on  insect  life.  Some  species  do 
best  in  dry  weather,  others  flourish  only  when  there 
is  an  abundance  of  moisture,  and  sometimes  a  sudden 
change  from  one  condition  to  another  will  produce  a 
complete  change  in  insect  conditions  within  twenty- 
four  hours.  Thripids  as  a  rule  require  dry  weather, 
and  after  a  period  of  drought  and  heat,  the  air  may 
be  full  of  the  little  creatures  not  over  an  eighth  of  an 
inch  in  length  and  so  slender  as  to  be  almost  invisible. 
A  cold  rain  lasting  a  few  hours  may  reduce  them  to 
so  small  a  number  as  to  make  them  practically  undis- 
coverable.  Agriculturists  sometimes  take  advantage 
of  this  peculiarity  by  spraying  infested  plants  with  cold 
water,  and  that  is  really  about  as  satisfactory  a  method 
of  control  as  we  have. 

Every  one  who  observes  nature  at  all,  has  probably 
noticed  that  in  some  seasons  insects  are  much  more 
abundant  than  they  are  in  others,  and,  more  specifi- 
cally, certain  kinds  may  be  almost  completely  absent 
or  on  the  other  hand  frightfully  abundant.  Now  in 
most  cases  these  differences  are  largely  and  in  some 
even  exclusively  due  to  climatic  conditions.  There 
is  no  greater  check  to  insect  life  than  adverse  weather, 
and  many  of  the  differences  in  abundance  attributed 
to  other  causes  are  really  due  to  climate. 


THEIR  RELATION  TO  WEATHER         143 

During  a  wet  spring  certain  species  of  plant  lice 
may  become  so  abundant  as  to  threaten  a  given  crop, 
with  their  natural  enemies  so  far  in  the  rear  as  to  seem 
hopelessly  out  of  the  running.  A  sudden  change  to 
hot  dry  weather  will  change  conditions  so  radically, 
that  within  a  week  the  lice  are  gone,  while  ladybird 
larvae  and  other  plant  louse  destroyers  are  feeding 
upon  each  other. 

No  kind  of  insect  is  more  sensitive  to  weather 
changes  than  are  the  Aphids,  and  few  of  them  are  able 
to  resist  a  sudden  change  of  temperature  exceeding 
30°  in  range;  but  an  increasev  is  not  nearly  so  fatal  to 
most  of  them  as  a  sudden  drop.  By  the  term  sudden 
I  mean  within  an  hour  or  two,  because  ranges  of  30°  or 
over  within  twenty-four  hours,  are* not  uncommon  in 
most  portions  of  the  United  States. 

The  character  of  the  winter  has  much  to  do  with 
the  abundance  of  insects  during  the  summer  following. 
It  is  not  so  much  the  hard  or  the  mild  winter  as  the 
variable  winter  that  is  fatal  to  insect  life.  When  an 
insect  goes  into  hibernation  in  either  larval  or  adult 
stage  it  becomes  torpid  and  capable  of  resisting  all 
usual  degrees  of  cold.  Even  if  the  cold  is  long  continued 
at  its  most  intense  point  it  makes  little  difference  and, 
in  general,  we  may  say  that  a  continuously  severe 
winter  is  favorable  to  insect  life.  The  insect  simply 
remains  torpid  and  no  change  in  condition  occurs.  On 
the  other  hand  if  there  are  alternations  of  freezing  and 
thawing,  the  insect  may  become  partially  or  altogether 
active  and  again  torpid,  losing  in  vitality  at  every 
change  until  it  dies  or  reaches  spring  in  such  condition 
as  to  be  unable  to  complete  its  tranformations  or  to 
reproduce  its  kind.  Such  alternations  are  particularly 
hard  on  pupae  and  on  larvae  that  winter  underground 
in  cells.  A  thaw  results  in  softening  the  ground  and 


144  INSECTS 

partially  disintegrating  the  walls  of  the  cell:  a  heavy 
frost  following  heaves  the  surface,  and  the  water  in 
the  soil  in  freezing  breaks  up  the  cells  completely, 
bringing  the  soil  into  direct  contact  with  the  soft  in- 
sects, crushing  or  otherwise  destroying  them. 

A  variable  winter,  therefore,  is  a  hard  one  on  insect 
life,  and  during  the  summer  following  certain  species 
are  likely  to  be  conspicuous  by  their  absence.  It  is 
such  factors  as  these  that  tend  to  limit  a  fauna;  only 
species  capable  of  withstanding  their  variations  being 
capable  of  continued  existence  under  them.  The  com- 
mon and  widely  distributed  species  are  those  that 
have  become  adapted  to  a  wide  range  of  tempera- 
ture and  relative  humidity;  the  others  are  more  lim- 
ited as  to  the  conditions  under  which  they  can  exist 
and  die  off  in  proportionately  large  numbers  when 
conditions  are  adverse. 

While  climatic  conditions  are  important  factors  in 
limiting  both  numbers  and  distribution,  they  are  per- 
haps more  effective  in  limiting  distribution,  since  the 
occurrence  of  a  species  within  a  faunal  region  presup- 
poses an  adaptation  to  its  normal  ranges  of  temperature 
and  moisture.  A  more  effective  agent  in  limiting  num- 
bers is  found  in  the  diseases  to  which  insects  are  subject, 
and  yet  the  effectiveness  of  diseases  as  a  check  is  in 
large  part  due  to  climatic  conditions,  most  of  them 
developing  best  or  only  in  moist  hot  weather. 

Insects  suffer  severely  from  epidemic  diseases  due 
to  micro-organisms — fungus  and  bacterial — and  of 
these  diseases  we  know,  as  yet,  comparatively  little.  Al- 
most every  observant  individual  has  seen  late  in  the 
season,  attached  to  a  window  pane,  specimens  of  the 
common  house-fly  with  abdomen  distended  and  a 
little  whitish  powder  surrounding  the  points  of  attach- 
ment. Such  flies  have  been  killed  by  a  disease  that  is 


THEIR  RELATION  TO  WEATHER          145 

contagious  and  frequently  kills  large  numbers  of  speci- 
mens. Grasshoppers  are  often  seen  dead  and  dry,  on 
top  of  some  stalk  of  grass  or  at  the  tip  of  some  weed, 
and  this  death  also  is  due  to  disease.  When  we  break 
up  such  a  grasshopper  we  find  it  filled  with  a  powdery 
mass — the  spores  of  the  disease  that  caused  death. 
Caterpillars  are  sometimes  found  presenting  a  peculiarly 
limp  appearance,  and  these  when  touched  prove  but  a 
pasty  mass  of  bacterial  organisms.  On  a  cabbage  leaf 
infested  by  plant  lice  we  may  almost  always  find  a 
portion  that  are  dull  yellowish-brown  in  color  and 
opaque:  victims  of  disease,  easily  distinguishable  from 
the  parasitized  examples  which  are  more  distended 
and  somewhat  shining  or  glazed.  And  so  in  every 
order,  attacking  either  larvae  or  adults,  there  are  dis- 
eases that  lie  in  wait  for  them  and  carry  off  large  per- 
centages. Some  of  these  diseases  have  been  long  known 
and  their  effectiveness  is  so  great  that  efforts  have  been 
made  to  propagate  with  the  view  of  using  them  prac- 
tically. But  it  was  found  that,  while  some  effect  was 
always  produced,  and  while  some  diseases  seemed 
equally  effective  year  after  year,  others  acted  only  when 
weather  conditions  were  just  right  and  were  therefore 
unreliable,  because  these  conditions  could  not  be  con- 
trolled even  though  the  germs  of  the  disease  might  be 
supplied. 

The  most  extensive  and  most  interesting  experi- 
ments of  this  nature  were  carried  on  a  few  years  ago  in 
some  of  the  states  of  the  central  west  against  the  chinch- 
bug,  which  is  one  of  the  most  serious  enemies  to  grain 
and  corn  culture  in  those  sections.  The  chinch-bug 
is  a  sucking  insect  belonging  to  the  order  Hemiptera, 
and  therefore  cannot  be  reached  by  any  stomach  poison. 
It  is  killable  by  certain  contact  insecticides,  but  the 
task  of  spraying  the  enormous  grain  and  corn  fields 


146  INSECTS 

of  Kansas  and  other  states  of  that  section  loomed  up 
so  large  and  expensive,  that  it  seemed  discouraging. 
In  the  exhaustive  study  carried  on  by  a  number  of 
entomologists,  it  was  noticed  that  the  species  was 
subject  to  certain  diseases  and  that  at  least  one  of 
these  was  often  epidemic  in  character  and  capable  of 
being  propagated.  The  suggestion  was  therefore  made 
that  this  disease  furnished  the  natural  method  for 
dealing  with  the  insect,  and  field  experiments  seemed 
to  bear  out  the  suggestion.  The  result  was  the  estab- 
lishment of  laboratories  for  the  propagation  and  dis- 
tribution of  chinch-bug  disease,  in  almost  every  state 
subject  to  chinch-bug  attack,  and  the  introduction  of  the 
disease  into  every  section  where  the  insect  occurred  in 
sufficient  numbers  to  attract  attention.  There  were 
some  wonderfully  successful  results  reported,  and  fully 
as  many  absolute  failures,  and  this  eventuated  in  the 
discovery,  after  much  patient  observation,  that  the 
chinch-bug  flourished  and  delighted  in  dry  weather, 
being  most  active  and  vigorous  in  droughty  times, 
when  the  food  plants  themselves  were  in  the  poorest 
condition  to  withstand  attack.  In  times  of  moisture 
the  bugs  were  sluggish,  inert,  and  low  in  vitality,  while 
the  plants,  on  the  other  hand,  were  vigorous  and  capable 
of  out-growing  and  resisting  injury.  The  disease,  on 
its  part,  would  not  develop  nor  spread  in  dry  weather 
when  the  bugs  were  most  troublesome;  but  it  did 
spread  like  wild-fire  in  a  wet  season  when  it  was  least 
needed.  As  a  dependence  to  check  the  spread  of  the 
insects  when  danger  was  imminent,  the  experiment  was 
a  failure;  but  the  practice  was  nevertheless  a  success, 
because  the  disease  has  now  been  introduced  every- 
where and  is  a  constant  danger  to  the  bugs,  reducing 
them  to  such  small  numbers  during  moist  seasons  that 
in  dry  seasons  there  are  not  enough  of  them  living  over 


THEIR  RELATION  TO  WEATHER          147 

to  become  dangerous.  It  would  now  require  a  series 
of  two  or  three  dry  seasons  in  succession  to  provide 
for  a  dangerous  outbreak.  And  this  seems,  in  a  way, 
to  measure  our  present  ability  to  use  diseases  as  a  check 
to  insect  increase,  i.e.,  we  can  plant  them  where  they 
will  lie  dormant  and  ready  to  fall  upon  the  insects 
whenever  conditions  become  favorable.  Our  knowl- 
edge is  as  yet  altogether  too  rudimentary  to  enable  us 
to  predict  future  possibilities. 

A  disease  of  the  grasshopper  has  been  referred  to, 
and  this  has  formed  a  subject  for  extensive  research 
work  in  South  Africa  where  the  migratory  forms  are 
among  the  most  destructive  pests.  It  was  found  that 
there  is  a  disease  that  sometimes  appears  among  the 
flying  hordes  and  destroys  enormous  numbers  of  them. 
This  disease  has  been  studied,  has  been  propagated  on 
culture  media,  and  has  been  distributed  in  pure  cultures 
with  directions  as  to  how  swarms  may  be  infected 
through  a  prepared  food.  They  depend  in  this  instance 
upon  infecting  bran,  meal  or  a  similar  material  with 
the  disease  culture,  to  be  exposed  where  the  wingless 
grasshoppers  will  find  and  eat  it.  They  thus  become 
inoculated  with  the  germs  and  establish  the  disease  in 
the  swarms  in  which  it  afterwards  spreads  naturally. 
The  results  on  these  South  African  forms  are  said  to 
be  very  satisfactory.  The  attempts  to  establish  the 
same  disease  in  our  American  species  have  not  produced 
any  marked  results  as  yet. 

Scale  insects  are  quite  subject  to  disease  attack, 
especially  in  climates  like  that  of  Florida,  where  certain 
of  the  armored  scales  are  kept  at  harmless  numbers  by 
fungi.  One  of  these  attacked  the  San  Jose"  or  pernicious 
scale  when  it  was  introduced  into  that  region,  keeping 
it  down  without  much  assistance  on  the  part  of  the 
fruit-growers.  Efforts  to  introduce  this  disease  into 


148  INSECTS 

Illinois  and  New  Jersey  succeeded  in  so  far  that  it  was 
actually  established,  but  proved  utterly  incapable  of 
catching  up  with  the  insects  during  the  hot  dry  spells 
of  midsummer  when  it  rested  dormant,  while  the  scale 
flourished  and  multiplied.  When  rains  came,  the  tem- 
perature fell  below  that  needed  by  the  disease,  and  we 
found  an  evident  case  of  climatic  limitation.  Evi- 
dences of  the  existence  of  the  disease  may  even  now 
be  found  in  New  Jersey  in  some  localities,  ten  years 
after  it  was  first  introduced;  but  it  never  yet  cleared 
even  a  single  tree  of  scales! 

This  brings  up  a  point  of  some  interest  and  much 
importance:  the  length  of  time  during  which  a  dis- 
ease may  lie  dormant  and  retain  its  virulence.  On  this 
point  our  information  is  very  scant;  but  an  example 
in  illustration  may  be  given.  The  periodical  Cicada, 
or  "  1 7 -year  locust"  as  it  is  more  popularly  known, 
is  attacked  in  the  adult  condition  by  a  fungus  disease 
that  attacks  the  body  of  the  male,  destroys  the  sexual 
organs  and  causes  the  abdomen  to  drop,  so  that  during 
the  latter  days  of  a  Cicada  invasion  a  large  percentage 
of  male  examples  will  be  found  mutilated  in  this  way. 
So  far  as  is  known  this  disease  attacks  no  other  insects, 
and  for  seventeen  years  it  lies  dormant,  somewhere, 
ready  to  become  active  again  when  a  new  brood  makes 
its  appearance. 

Certain  kinds  of  plant  lice  are  always  more  or  less 
attacked  by  disease,  and  some  show  more  diseased 
than  parasitized  specimens  at  all  times.  Indeed  I  am 
inclined  to  believe  that,  aside  from  temperature  con- 
ditions, diseases  are  the  most  effective  of  all  checks  to 
plant  lice  increase;  but  so  far  as  I  am  aware,  no  at- 
tempts have  yet  been  made  to  use  any  of  them  prac- 
tically. Perhaps  I  should  guard  myself  here  against 
being  misunderstood.  I  am  quite  aware  that  some 


THEIR  RELATION  TO  WEATHER         149 

species  of  plant  lice  are  so  heavily  parasitized  that 
even  when  they  get  a  good  start  early  in  the  year, 
their  enemies  usually  overhaul  them  before  they  have 
destroyed  or  even  severely  injured  their  host  plant; 
nevertheless  I  am  ready  to  allow  my  statement  to  stand 
as  an  expression  of  general  conditions,  applicable  to 
the  ordinary  run  of  species. 

I  have  already  referred  to  the  fact  that  caterpillars 
are  subject  to  disease  and  the  check  to  certain  species 
is,  I  believe,  much  greater  than  is  generally  recognized. 
On  that  point  I  made  a  very  interesting  study  on  a 
large  series  of  light  cocoons  of  the  Cecropia  moth, 
finding  that  more  than  two  thirds  of  all  the  caterpillars 
died  of  some  trouble  other  than  parasites  after  the 
cocoons  had  been  completed,  but  before  the  change 
to  pupa  had  taken  place.  Others  as  well  as  I  have 
observed  entire  broods  of  caterpillars  dying,  and  one 
of  the  characteristic  attitudes  of  such  diseased  cater- 
pillars is  that  the  twig  or  leaf  is  clasped  by  the  pro- 
legs  along  the  sides  of  the  body,  while  the  portions 
anterior  and  posterior  to  this  hang  limp  and  lifeless. 
Eventually  the  whole  thing  dries  and  shrivels  up  almost 
to  a  skin.  This  sort  of  condition  I  observed  in  Massa- 
chusetts in  1907,  in  territory  infested  by  gypsy  and 
brown-tail  moths;  fully  50  per  cent,  of  all  the  larvae 
seen  showing  evidences  of  disease:  and  that  condition 
existed  to  a  still  greater  extent  in  1906,  when  a  large 
proportion  of  the  caterpillars  of  the  brown-tail  moth 
were  wiped  out  of  existence. 

This  is  eminently  one  of  those  cases  where  an  ear- 
nest effort  should  be  made  to  use  the  disease-producing 
organisms  to  check  increase  and  spread,  and  the  study 
of  the  subject  has  been  actually  taken  up.  It  is  quite 
probable  that  it  will  be  found  that  the  disease  has  its 
limitations,  and  that  it  requires  certain  climatic  con- 


iSo  INSECTS 

ditions  for  its  greatest  efficiency.  But  we  can,  at  least, 
follow  up  the  spread  of  the  insects  with  the  disease, 
and  by  getting  the  germs  into  every  colony  as  fast  as 
it  is  established,  introduce  a  check  which  is  ready  to 
act  when  conditions  become  favorable,  and  which  may, 
in  some  localities,  control  it  absolutely. 

Only  a  small  number  of  insects  have  been  specifi- 
cally mentioned  as  suffering  from  disease  attack; 
but  this  does  not  begin  to  indicate  the  actual  extent 
to  which  they  suffer,  nor  the  varying  character  of  the 
infestations.  And  it  is  not  only  those  species  that  live 
above  ground  on  trees  or  foliage  that  are  affected. 
Some  of  the  underground  forms  like  white  grubs,  wire- 
worms  and  others  are  subject  to  the  attacks  of  growths 
which  change  the  entire  insect  into  a  corky  mass,  giving 
rise  in  some  cases  to  processes  that  reach  above  ground 
as  though  the  grub  itself  had  begun  to  sprout.  The 
extent  to  which  such  conditions  occur  we  cannot  esti- 
mate because  they  are  mostly  out  of  our  view;  but  we 
do  not  find  them  often  enough  to  indicate  that  they  ex- 
ercise any  great  influence  upon  the  number  of  examples 
that  come  to  maturity. 

Among  aquatic  insects  diseases  also  occur,  and  I 
have  frequently  lost  entire  broods  of  mosquito  larvae 
that  have  been  the  subject  of  some  trouble  which  caused 
a  cheesy  degeneration. 

Every  breeder  of  insects  has  had  some  of  his  cages 
infected  with  disease  germs  so  that  every  brood  sub- 
sequently introduced  died  off  altogether  or  in  large 
part,  and  the  experienced  man  to  whom  this  happened 
destroyed  those  cages  altogether  if  he  could,  or  cleaned, 
disinfected  and  exposed  them  to  the  action  of  the  sun 
and  air  if  for  any  reason  keeping  them  was  necessary. 
He  realized  that,  once  established,  a  germ  disease  was 
extremely  difficult  to  get  rid  of  by  any  but  the  most 


THEIR  RELATION  TO  WEATHER         151 

drastic  measures.  Many  years  ago  the  breeders  of  silk- 
worms in  France  found  their  caterpillars  dying  at  such 
a  rate  as  to  threaten  the  very  existence  of  the  industry. 
It  was  a  germ  disease  of  course,  but  nothing  was  known 
of  such  things  at  that  time  and  it  afforded  an  oppor- 
tunity for  Pasteur  to  win  renown  and  to  benefit  his 
fellows  to  a  degree  that  few  in  that  or  any  other  country 
have  really  appreciated.  It  gave  a  striking  illustration 
of  what  epidemic  disease  could  do  under  favorable 
conditions,  and  it  is  still  suggestive  as  to  possibilities 
when  we  attempt  to  reverse  the  Pasteur  objective. 

At  the  present  time  many  bee-colonies  are  suffering 
from  what  is  known  as  "foul-brood,"  a  disease  or  dis- 
eases of  micro-organic  origin  which  carries  off  enormous 
numbers  of  specimens  annually.  The  character  of  the 
organisms  causing  these  diseases  is  now  known  and, 
in  a  general  way,  the  treatment  to  be  adopted,  so  there 
is  nothing  at  all  mysterious  except  the  negligence  of 
the  bee-keeper  who  permits  the  disease  to  develop  un- 
checked in  so  many  instances.  It  is  probably  rare  that 
an  insect  once  attacked  by  disease,  recovers.  In  my 
breeding  experiences  and  in  field  observations  I  have 
never  known  of  such  a  case.  I  have  often  seen  among 
a  brood  that  sickened,  one  or  a  very  few  individuals 
that  showed  no  trace  of  disease,  that  fed  normally 
and  developed  naturally;  but  I  have  never  seen  such 
a  larva  show  signs  of  the  sickness  and  then  resume 
growth;  so  in  a  general  way  these  diseases  may  be  con- 
sidered as  fatal  when  they  once  gain  a  foothold. 

We  have  now  seen  that,  while  in  general  there  are 
no  conditions  of  climate  where  insects  do  not  occur, 
yet  climatic  conditions  may  and  do  in  many  cases 
check  not  only  the  distribution  but  the  numbers  of 
insects:  that  while  many  species  are  fitted  to  live  under 
widely  varying  conditions,  others  are  adaptable  within 


152  INSECTS 

very  narrow  limits  only,  and  succumb  readily  to  vari- 
ations beyond  the  normal  range. 

We  have  seen  also  that,  not  only  dp  insects  suffer 
from  germ  diseases,  but  that  these  ofteft  assume  the 
dimensions  of  epidemics  and  form  a  very  important 
factor  in  nature's  scheme  of  insect  control;  a  factor  of 
which  we  have  not  yet  made  the  utmost  possible  use 
in  our  dealing  with  the  economically  important  species. 


CHAPTER  VII 

THEIR  RELATION  TO  OTHER  ANIMALS 

IN  the  course  of  their  development  insects  have 
established  the  closest  kind  of  relations  to  the  rest  of 
the  animal  kingdom,  and  there  is  scarcely  a  vertebrate 
terrestrial  animal  that  is  not  more  or  less  affected  by 
parasites — man  not  excluded.  Some  of  this  parasitism 
is  of  the  most  highly  specialized  character.  We  have 
somehow  come  to  think  of  parasites  as  being  simple, 
lowly  organized  creatures,  of  very  inferior  rank,  and 
yet  a  moment's  thought  will  show  that  there  could  be 
no  parasites  of  vertebrates  un.til  the  vertebrates  them- 
selves existed,  and  as  the  insects  long  antedated  verte- 
brates, parasitism  must  have  come  as  a  specialization 
from  an  already  well-developed  organism. 

Nor  is  such  parasitism  confined  to  what  we  call  the 
lower  orders,  for  we  find  none  of  it  in  the  Thysanura 
or  primitive  forms;  but  its  most  elaborate  development 
occurs  in  the  Diptera,  or  flies,  which  are  the  highest  in 
the  scale  so  far  as  physiological  specialization  goes. 

As  might  be  supposed,  the  Hemiptera,  gaining  their 
food  by  piercing  and  sucking,  rank  well  among  the 
orders  containing  animal  parasites;  indeed,  broadly 
speaking,  a  large  percentage  of  the  order  is  strictly 
parasitic  on  either  plants  or  animals.  The  scale  insects, 
for  instance,  are  absolutely  dependent  upon  the  host 
plants  to  which  they  attach  themselves,  and  many  of 
them  if  once  removed  from  their  attachment,  are  help- 
less and  die.  The  plant  lice  are  less  strictly  parasitic 
and  yet  the  term  "lice"  is  a  good  one  when  we  compare 
it  with  the  same  term  used  for  those  suckers  that  feed 


154 


INSECTS 


on  vertebrate  blood.  But  the  parasitism  here  is  of  an 
exceedingly  simple  character,  and  means  only  the 
adaptation  of  the  external  form 
to  a  life  among  fur,  hair  or 
feathers,  and  the  development 
of  some  sort  of  structures  to 
hold  on  with. 

Most  hairy  animals,  from  the 
little  field  mouse  through  all  the 
ruminants  to  man  himself,  are 
subject  to  the  attacks  of  sucking 
lice.  Now,  while  man  cannot  be 
strictly  ranged  as  a  hairy  animal 
nowadays,  some  of  his  anthro- 
poid allies  come  conveniently 
under  such  a  definition,  and  the 
few  species  that  infest  humanity 
are  some  of  the  remaining  dis- 
advantages of  a  former  closer 
relationship  with  ape-like  forms. 
That  man  has  been  in  this  com- 
paratively hairless  condition  for 
a  long  time  is  shown  by  the  fact 
that  one  of  his  parasites  has  be- 
come especially  adapted  to  life 
under  such  conditions,  and  that 
another  has  undergone  an  even 
more  profound  modification  in 
habit  since  he  was  a  clothed 
animal. 

These  sucking  lice  are,  in 
general,  small  flattened  creat- 
ures, gray,  whitish  or  yellowish 
in  color,  with  an  elongate  oval  body  or  abdomen  cov- 
ered with  short  hair  or  spines,  and  a  more  or  less 


FlG'  ^ 


°f  a 


RELATION  TO  OTHER  ANIMALS  155 

pointed  head  from  which  a  pair  of  slender  styles  or 
lancets  may  be  protruded.  In  many  cases  there  is  at 
the  base  of  these  sucking  structures  a  series  of  recurved 
hooks  or  small  horny  processes,  by  means  of  which  the 
creature  anchors  itself  in  the  tissue  of  its  host  and  sucks 
at  its  convenience.  Such  structures  are  apt  to  be  devel- 
oped in  forms  infesting  animals  with  rather  scant  short 
hair,  where  some  method  of  holding  fast  is  desirable. 
Another  development  is  on  the  feet,  where  the  tarsal 


FIG.  64. — a,  body  louse  of  man;   b,  hog  louse;  c,  head  louse  of  man. 


joints  are  arranged  so  as  to  be  opposable  to  the  end 
of  the  tibia,  like  a  thumb.  In  this  structure  an  in- 
dividual hair  is  seized  and  held  so  tightly  that  it  may  be 
pulled  from  its  socket  sooner  than  the  insect  from  it. 
This  type  has  been  called  "scansorial"  or  climbing, 
because  the  insect  moves  about  by  grasping  the  hair 
nearest  to  its  position  and  pulling  itself  along  from  one 
foothold  to  another.  An  extremely  pretty  illustration 
of  this  sort  is  found  in  the  hog  louse,  and  another  in 
the  crab  louse  of  man. 

By  far  the  greater  number  of  these  parasites  attach 
their  eggs  directly  to  the  hair  or  bristles  of  their  host, 


156  INSECTS 

and  pass  their  entire  life  upon  it.  They  are  incapable 
of  existence  away  from  this  host  and  have  no  power 
of  gaining  food  from  any  other  source.  The  young 
are  not  very  different  except  in  size,  from  the  adults, 
and  there  is  no  obvious  metamorphosis. 

Three  species  live  on  man  and  their  distribution 
is  coincident  with  that  of  humanity.  The  head  louse, 
Pediculus  capitis,  lives  among  the  longer  hair  of  the 
body,  usually  confined  to  the  head.  Its  legs  are  not 
scansorial,  it  has  the  anchoring  process  at  the  base  of 
the  head  well-developed,  and  the 
eggs  or  "nits"  are  attached  to  the 
hair.  The  crab  louse,  Phihirius  in- 
gumaiis,  lives  among  the  coarser,  less 
abundant  hair  of  the  pubic  and  ax- 
illary regions  and  in  hairy  individ- 
uals also  on  other  parts  of  the  body. 
The  legs  here  are  scansorial,  as  of 
FIG.  65.— An  egg  or  necessity  they  must  be  to  enable  the 
nit,  attached  to  a  hair.  insect  to  maintain  itself ,  and  it  also 
glues  its  eggs  to  the  hair  among 
which  it  lives.  The  body  louse,  Pediculus  vestimenti, 
lives  among  the  thinner  body  hair  and  almost  alto- 
gether on  parts  normally  covered  by  clothing.  Its  legs 
are  not  well  fitted  for  grasping,  but  the  anchor  proc- 
esses of  the  mouth  are  well  developed.  The  peculiarity 
of  this  species  is  that  it  remains  on  the  body  of  the  host 
only  while  it  is  feeding  and  at  other  times  hides  in  his 
clothing,  where  also  it  deposits  its  eggs.  Man,  there- 
fore, has  worn  clothing  for  a  period  long  enough  to 
enable  this  parasite  to  adapt  its  mode  of  life  to  this 
habit,  and  to  depend  upon  his  garments  for  protection 
and  as  a  nidus  for  its  ova. 

These     parasites     sometimes     become     exceedingly 
abundant   when   men   are   herded   together  in   camps, 


RELATION  TO  OTHER  ANIMALS          157 

ships,  or  prisons,  and  specific  irritations  known  as 
Pediculosis  and  Phthiriasis  are  produced  by  them. 
It  has  been  calculated  that  a  single  adult  female  of 
the  body  louse  might  have,  in  eight  weeks,  a  progeny 
of  5000,  and  while  this  is  not  equal  to  the  performances 
of  some  other  insects  it  does,  nevertheless,  serve  to 
make  possible  a  very  rapid  and  complete  infestation 
where  they  are  allowed  to  develop  unchecked. 

Of  course  personal  cleanliness  is  the  best  of  all 
methods  to  be  and  become  free  from  such  parasitism; 
but  infestation  in  modern  conveyances  is  always  pos- 
sible, and  with  even  the  greatest  care  a  parasite  may 
obtain  a  foothold.  Children,  who  are  not  always  choice 
in  their  companions,  not  infrequently  become  infested 
by  head  lice.  A  fine-tooth  comb  and  a  thorough  greas- 
ing of  the  hair  with  pomade  or  any  fatty  material, 
repeated  twice  at  intervals  of  a  week  each,  will  clear 
out  the  parasites.  The  grease  enters  into  and  clogs 
the  breathing  pores  of  the  lice  and  chokes  them;  but 
it  does  not  affect  the  eggs  or  -'nits."  The  later 
applications  are  intended  to  reach  the  young  that 
have  hatched  from  the  eggs  since  the  previous  ones. 
As  the  eggs  may  remain  unhatched  for  ten  days  or 
two  weeks,  this  period  of  time  will  be  necessary  to 
insure  freedom. 

As  for  the  body  louse,  the  infested  clothing  should 
be  discarded  for  a  time.  Underclothing  may  be  sub- 
jected to  lengthy  boiling  to  kill  both  adults  and  eggs. 
Outer  garments  should  be  steamed  or  baked  if  possible, 
or  should  be  dipped  into  gasoline;  this  latter  applica- 
tion to  be  repeated  in  ten  'days,  to  reach  later  hatchings. 
The  gasoline  process  is  simplest  as  it  kills  all  the  adults 
at  once,  and  if  it  can  be  repeated  at  short  intervals, 
the  clothing  can  be  worn  in  the  periods  between 
treatments. 


158  INSECTS 

The  crab  louse  is  treated  by  local  applications  of 
mercurial  ointment  or  by  tincture  of  larkspur  (Del- 
phinium), the  latter  of  which  is  also  used  against  the 
head  louse. 

The  habit  that  some  savages  have  of  covering  them- 
selves with  grease,  oil  or  paint,  is  not  entirely  without 
practical  advantage,  for  thereby  they  do  undoubtedly 
keep  themselves  measurably  free  from  these  parasitic 
forms.  The  use  of  ants  to  rid  infested  clothing  of  para- 
sites is  referred  to  by  Mark  Twain  in  his  inimitable 

way,  and  it  was  a  recognized 
practice  in  the  far  west  in 
olden  days,  when  changes  of 
clothing  were  not  readily  ob- 
tainable, and  when  lodgings 
and  lodgers  could  not  be 
chosen  but  had  to  be  ac- 
cepted as  found.  It  meant 
•simply  stripping  naked,  and 
FIG.  66.— Crab  louse  of  man.  placing  all  the  clothing  on 

an  ant  hill,  where  it  would 

be  immediately  invaded  by  the  ants  anxious  to  attack 
and  destroy  every  living  thing  on  or  in  this  foreign 
material.  In  a  short  time  the  clothing  could  be  again 
put  on  with  the  comforting  assurance  that  it  was  at 
least  temporarily  free. 

Most  of  our  hairy  domestic  animals  are  subject  to 
the  attacks  of  similar  parasites,  each  of  which  lives 
and  propagates  on  the  body  of  its  respective  host. 
Spread  from  one  animal  to  another  occurs  when  they 
are  in  contact  in  stables,  or  herded  closely  together  for 
shade  in  the  pasture.  Sometimes  a  parasite  leaves 
its  host  voluntarily  or  is  rubbed  off  by  it  in  the  stable, 
kennel  or  field.  It  may  then  crawl  about  on  woodwork, 
plant  or  tree,  hiding  in  crevices  until  another  host 


RELATION  TO  OTHER  ANIMALS  159 

animal  comes  into  such  a  position  as  to  enable  it  to 
crawl  among  the  hair  or  wool. 

As  uncivilized  man  greases  or  paints  himself,  so 
animals  have  developed  a  method  for  securing  freedom 
from  parasites:  they  dust  themselves  or  coat  them- 
selves with  mud.  The  spiracles  of  most  lice  are  not  well 
protected,  so  when  animals  get  into  a  dusty  road  and 
roll  about,  this  serves  a  very  practical  purpose  and 
those  that  get  into  a  mud  hole  and  wallow  are  often 
seeking  similar  relief.  Other  species  of  Hemiptera 
preying  upon  man  will  be  considered  under  the  heading 
of  household  pests. 

Besides  the  sucking  lice  belonging  to  the  order 
Hemiptera,  many  animals  and  most  birds  are  also  sub- 
ject to  the  attacks  of  biting  lice,  belonging  to  the  order 
Mallophaga,  which  means,  literally,  wool-eaters,  and 
is  somewhat  misleading.  Commonly  they  are  also 
known  as  "bird-lice"  because  they  very  usually  infest 
the  feathered  tribe.  In  color  and  appearance  they  do 
not  much  differ  from  the  sucking  lice;  but  the  head 
is  usually  more  blunt,  and  instead  of  puncturing  the 
skin  and  living  on  blood,  they  have  mouth  parts  formed 
for  chewing  and  biting,  and  live  rather  on  the  surface 
scales  and  scurf  at  the  roots  of  the  hair  and  feathers. 
They  do  not  puncture  the  skin  to  reach  blood,  but  will 
feed  on  clotted  blood  at  the  edge  of  any  wound  and  may 
prevent  healing,  or  even  cause  the  extension  of  a  sore 
spot.  And  so,  while  a  few  individuals  on  the  skin 
cause  little  inconvenience  or  unpleasant  effect,  yet 
when  a  great  number  are  at  work,  the  feeding  at  the 
base  of  the  hair  and  of  the  smaller  feathers  results  in 
the  death  of  these  out-growths  and  the  infested  animal 
becomes  "mangy"  in  appearance.  The  true  mange 
is,  of  course,  due  to  a  mite  parasite  of  quite  a  different 
kind;  but  that  "mange"  which  consists  of  bare  spots 


i6o 


INSECTS 


on  a  hairy  animal  or  thin  plumage  on  a  chicken  or 
other  bird,  is  very  apt  to  be  due  to  biting  lice.  In  breed- 
ing habits  they  resemble  the  Pediculids  very  nearly; 
the  eggs  are  fastened  to  the  hair  or  feathers  and  there 
is  little  apparent  change  in  outward  appearance  from 
the  nymph  just  out  of  the  egg,  to  the  adult  ready  to 
reproduce.  None  of  these  species  are  found  on  man; 
but  nearly  all  farm  animals  and  all  the  domesticated 
birds  are  likely  to  become  infested,  each  with  its  own 


A  ''fl    ~  B 

FIG.  67. — a,  chicken  louse;   b,  turkey  louse. 


peculiar  species.  It  is  rare  that  one  species  of  parasite 
is  found  on  two  species  of  animals  not  very  closely 
allied;  but  it  is  not  uncommon  for  a  single  species  of 
animal  to  harbor  two  or  more  kinds  of  parasites. 

Birds  are  as  fond  of  a  powder  bath  as  are  the  four- 
footed  animals,  and  poultry  keepers  have  long  recog- 
nized the  importance  of  the  dust  box  in  keeping  their 
charges  in  good  condition.  It  should  always  be  the 
finest  of  dust  available  and  there  should  always  be 
plenty  of  it  in  a  box  of  generous  size  so  that  even  the 
largest  bird  can  cover  itself  thoroughly  without  scat- 
tering the  material  beyond  the  edge  of  the  container. 


RELATION  TO  OTHER  ANIMALS 


161 


Horses  and  cattle  can  be  very  readily  freed  from 
lice  parasites  by  a  free  use  of  curry-comb  and  brush, 
and  if  occasionally  the  brush 'be  dipped  into  a  pan  of 
crude  petroleum  so  that  the  tips  of  the  bristles  become 
wet,  the  coat  of  the  animal  will  be  materially  improved, 
and  any  louse  that  is  hit  will  be  killed.  Kerosene  must  not 
be  used  because  that  is  likely  to  kill  the  hair ;  but  crude 
petroleum  acts  as  a  stimulant  and  improves  its  growth. 

There  are  no  animal  parasites  in  the  other  Neurop- 
terous  orders,  and  in  the  great 
order  Coleoptera  or  beetles  there 
are  very  few.  We  have  scaven- 
gers and  feeders  on  dead  and  de- 
caying material  in  great  abund- 
ance, and  many  beetles  live  with 
specific  animals  in  very  close  re- 
lationship ;  but  very  few  actually 
occur  on  the  animals  themselves. 
In  the  United  States  the  mem- 
bers of  the  family  Platypsyllidce 
and  LeptinidcB  are  known  to  live 
on  the  beaver  and  a  few  other  ro- 
dents that  have  a  dense  fur. 

Just  what  the  relation  of  these  parasites  is  to  the  host 
is  not  entirely  clear,  but  the  larvse  do  not  live  on  it, 
and  feed  rather  on  the  waste  material  in  the  nests. 

Animal  parasites  would  scarcely  be  expected  among 
the  order  Lepidoptera,  or  butterflies  and  moths,  and 
strictly  speaking  there  are  none.  Yet  it  is  certain  that 
some  of  the  small  moths  belonging  to  the  Tineids, 
which  include  our  "clothes  moths,"  do  actually  breed 
and  develop  in  the  fur  or  wool  of  animals  like  the  sloth, 
certain  sheep,  etc.  There  is  such  a  thing,  then,  as  a 
fur  or  pelt  becoming  moth-eaten,  even  while  it  still 
covers  the  body  of  its  owner, 
ii 


FIG.  68.  —  Platypsylla  cas- 
toris:  parasite  on  beaver.  After 
Westwood. 


i62  INSECTS 

The  great  order  Hymenoptera,  in  which  insect  para- 
sitism is  developed  to  a  remarkable  extent,  contains 
no  species  that  live  on  vertebrate  animals. 

The  Diptera,  or  flies,  on  the  other  hand,  in  which 
specialization  has  been  almost  as  extreme  as  in  the 
Hymenoptera,  have  developed  a  considerable  number 
of  forms  that  depend  for  their  living  entirely  upon  the 
higher  animals. 


FIG.  69. — A  rabbit  flea. 

The  little  family  of  fleas,  which  are  very  highly 
specialized  flies,  although  now  usually  classed  in  an 
order  by  themselves,  are  all  parasites  on  warm-blooded 
animals  covered  with  hair  or  feathers.  They  are  small, 
brown,  transversely  flattened,  set  with  spines  or  stiff 
hair  directed  backward,  and  the  legs  are  powerful, 
fitted  for  jumping.  This  characteristic  form  makes  it 
very  easy  for  them  to  move  about  among  the  hair  and 
feathers,  and  this  they  do  in  a  sort  of  jerky  way  as  if 
they  were  making  short  jumps,  each  of  which  carries 
them  a  shorter  or  longer  distance  and  enables  them 


RELATION  TO  OTHER  ANIMALS 


163 


to  easily  avoid  the  paw  or  foot  of  the  animal  when  it 
scratches  the  place  where  it  feels  a  bite.  Although 
parasitic  in  so  far  as  it  lives  during  its  adult  stage  upon 
the  host  animal,  yet  the  insect  moves  about  freely, 
and  the  early  stages  are  passed  in  most  if  not  all  cases 
among  the  litter  in  the  nest  or  den  of  the  host,  and  not 
on  its  body.  In  its  early  stages,  then,  the  flea  is  not  a 


FIG.  70. — The  jigger  flea:  a,  normal  female;  b,  distended  with  eggs;  c,  larva. 


parasite,  but  rather  a  scavenger;  in  its  adult  stage  it 
feeds  on  blood  and  differs  from  mosquitoes  and  other 
flies  that  have  the  same  habit,  chiefly  in  remaining  on 
the  host  animal  during  the  period  when  it  is  not  feed- 
ing. As  soon  as  an  animal  is  dead  and  cold  the  fleas 
leave  it.  Of  fleas  in  their  relation  to  man  there  will  be 
more  to  say  in  a  later  chapter. 

There  is  one  little  group  of  fleas  roughly  known  as 
"jiggers"  that  depart  somewhat  from  the  normal  life 
history.  In  these  species  the  female  after  copulation 
seeks  some  host  into  which  it  may  burrow  or  imbed 


1 64  INSECTS 

itself.  Any  animal,  including  man,  will  serve,  and 
entrance  is  usually  made  between  the  toes  or  under 
toe-nails  or  claws,  because  penetration  is  easiest  there. 
When  once  in  position  under  the  skin,  the  body  of  the 
female  enlarges  as  the  eggs  develop  until  it  is  as  big 
as  a  pea  in  an  extremely  painful  and  usually  festering 
tumor.  The  eggs,  when  ready  to  be  laid,  are  discharged 
into  the  sore,  and  the  wriggling  larvae  make  their  way 
out  as  best  they  can,  to  develop  as  do  others  of  their 
kind.  Animals  often  suffer  severely  from  the  attacks 
of  these  pests  which  inhabit  the  southern  parts  of  our 
country  and  the  tropics,  and  man  is  not  infrequently 
attacked  where  he  goes  bare-footed.  Where  "jiggers" 
are  well  known  the  nature  of  the  attack  is  usually  recog- 
nized at  once,  and  the  insect  removed  with  a  needle  or 
a  knife-point;  sometimes  a  wet  quid  of  tobacco  is  tied 
over  the  infested  spot  for  a  few  hours,  and  this  softens 
the  skin  and  usually  kills  the  pest  so  that  removal  is 
easy.  If  the  matter  is  neglected  and  removal  is  not 
attempted  until  the  eggs  are  developed,  the  work  must 
be  carefully  done  so  as  to  avoid  breaking  the  body  of 
the  female  and  discharging  the  eggs  into  the  wound. 
Usually,  on  domestic  animals,  cleanliness  and  the 
free  use  of  lime  where  the  larvae  breed  is  sufficient  to 
avoid  trouble.  But  in  some  sandy  regions  fowls  suffer 
severely  from  the  species  that  attacks  them.  The  hen 
flea  is  an  ally  of  the  "jigger"  and  while  it  does  not  bore 
into  the  tissue  of  the  bird,  the  female  does  fasten  itself 
firmly  into  the  skin  and  remains  attached  until  dis- 
turbed by  some  outside  force.  On  young  chicks  they 
often  fasten  to  the  head  and  neck  in  such  numbers  as 
to  kill  their  host.  A  free  use  of  carbolated  vaseline  is 
indicated  in  cases  of  that  kind.  This  material  not  only 
kills  the  fleas  but  acts  as  a  disinfectant  and  promotes 
the  healing  of  the  sores. 


RELATION  TO  OTHER  ANIMALS          165 

There  are  many  other  kinds  of  fleas  and  they  infest 
almost  every  sort  of  animal  capable  of  affording  them 
shelter;  but  there  is  a  very  general  ..agreement  in  life 
history  and  in  the  character  of  the  methods  to  be  used 
in  their  control  when  control  becomes  a  matter  of  im- 
portance. Some  further  word  concerning  these  in-sects 
as  carriers  of  disease  will  be  found  in  a  subsequent 
chapter,  where  also  the  closer  relation  of  those  fleas 
that  occasionally  occur  in  our  houses  is  more  fully 
elucidated. 


FIG.  71. — Chicken  flea. 

Among  the  true  flies  there  are  a  great  number  of 
species  that  prey  upon  vertebrate  animals,  and  they 
do  this  in  two  ways:  either  by  feeding  upon  them  in 
the  adult  stage  alone,  or  by  actually  living  upon  them 
in  early  stages,  and  thus  becoming  true  parasites.  As 
the  flies  are  among  the  most  recent  of  insects,  so  their 
relations  to  the  vertebrates,  the  most  recent  develop- 
ments in  the  higher  animals,  are  also  most  close. 

The  simplest  form  of  relationship  is  that  afforded 
by  the  various  blood-sucking  flies — the  mosquitoes, 
gnats,  midges,  horse-flies,  stable  flies  and  others  allied 
to  them.  In  all  these  species  the  mouth  structures 
are  developed  into  a  series  of  long  slender  lancets 


1 66  INSECTS 

formed  so  as  to  be  able  to  Duncture  the  skin  of  the  host 
and  to  suck  the  blood  beneath  it.  In  almost  every 
instance  the  early  stages  are  passed  elsewhere  than  on 
the  host  that  serves  as  food  in  the  adult  stage,  and  some- 
times not  even  in  the  same  medium.  The  mosquitoes, 
for  instance,  attack  all  sorts  of  vertebrates,  cold-blooded 
as  well  as  warm-blooded;  but  so  far  as  known,  all  the 
larvae  are  strictly  aquatic,  dwellers  in  water  and  adapted 
to  secure  their  food  only  in  that  medium.  Yet  while 
the  direct  relations  between  animals  and  mosquitoes 
are  simple  enough,  the  indirect  influence  that  they 
exert  as  intermediate  hosts  for  certain  disease-produc- 
ing organisms  are  of  so  great  importance  as  to  require 
more  specific  treatment  in  another  connection. 

The  Simuliidce,  containing  those  species  known  as 
"black  flies,"  "midges,"  "Buffalo  gnats"  and  others 
of  similar  character,  are  in  somewhat  the  same  case. 
The  adults  feed  on  warm-blooded  animals,  the  larvae 
are  found  only  in  water  usually  adhering  to  stones, 
logs,  roots  or  other  points  of  attachment  and  gaining 
their  food  supply  entirely  from  beneath  the  surface. 
As  both  mosquitoes  and  gnats  develop  in  water,  their 
presence  as  adults  in  some  localities  is  coincident,  and 
a  better  combination  for  making  life  miserable  can 
scarcely  be  imagined.  The  gnats  are  preferably  day 
fliers,  the  mosquitoes  preferably  night  fliers,  so  the 
entire  diurnal  cycle  is  thus  provided  for.  The  "black 
flies"  do  not  worry  their  victims  by  buzzing  or  "sing- 
ing." They  are  extremely  business-like  in  their  method 
and  as  soon  as  they  alight  they  set  to  work.  Their 
puncture  is  recognizable  at  once  and  resembles  the 
prick  of  a  hot,  very  fine  needle,  much  more  than  any 
other  bite  known  to  me.  The  mouth  parts  are  short, 
not  nearly  so  compact  as  those  of  the  mosquitoes,  and 
the  flies  appear  to  veritably  dig  into  the  skin  leaving, 


RELATION  TO  OTHER  ANIMALS          167 

when  driven  off,  a  wound  large  enough  to  bleed — a 
butchery  of  which  no  mosquito  is  ever  guilty.  The 
small  black  flies,  usually  called  "midges,"  are  not  con- 
tent to  attack  only  the  exposed  parts  of  the  body: 
they  crawl  into  the  ears,  the  nose,  under  the  clothing 
at  the  ankles,  wrists  or  neck,  and  where  a  novice  goes 


FIG.  72. — "Buffalo  gnat"  or  "black  fly." 

unprepared  into  an  infested  territory,  he  usually  stays 
there  only  as  long  as  is  absolutely  necessary.  Even 
the  veteran  is  sometimes  forced  to  run  when  he  has  not 
provided  himself  with  some  repellant  substance.  Of 
these  "dopes"  there  are  various  sorts  known  to  the 
woodmen,  and  their  basis  is  usually  a  cotton-seed  or 
olive  oil,  with  an  admixture  of  oil  of  tar,  oil  of  penny- 
royal, menthol  or  some  similar  volatile  oil.  Oil  of 
citionella  is  in  great  favor  with  many  and,  in  my  own 


1 68 


INSECTS 


experience  is  a  little  the  most  satisfactory  and  agree- 
able. The  odor  is  offensive  to  others,  however,  and 
these  may  find  the  menthol  preparations  more  satis- 
factory. Cattle  and  animals  not  being  able  to  resort  to 
repellants  often  suffer  cruelly,  and  in  countries  where 
buffalo  and  similar  larger  gnats  are  plentiful,  they 
are  sometimes  driven  literally  insane  by  the  pain  and 

irritation  of  the  attack. 

The  early  stages  being 
passed  continually  under 
the  water  surface,  offer  no 
points  for  an  attack  with 
oils.  No  matter  how  the 

1    PHI  ^^K^^  uPPer  la^er  ma^  be  coat~ 

J    (M  ed,  the  insects  on  the  bot- 

torn  will  be  little  or  not  at 
all  disturbed,  and  as  they 
usually  inhabit  running 
streams,  it  is  practically 
impossible  to  maintain  a 
surface  covering  anyhow. 
Those  species  that  attach 
themselves  to  logs  and 
sunken  or  surface-lodged 

tree  trunks  or  the  like,  may  be  mitigated  by  cleaning 
but  such  obstructions  and  points  of  attachment;  but 
for  such  species  as  attach  themselves  to  stones  on  the 
bottom  we  have  no  remedy  that  is  not  also  likely  to  be 
fatal  to  fish  and  other  forms  of  aquatic  life.  Thus  far 
no  charge  has  ever  been  made  against  any  of  the 
Simuliidce  that  they  are  carriers  of  disease  in  man  or 
animals ;  but  our  actual  acquaintance  with  the  flies  and 
with  the  diseases  of  the  animals  that  inhabit  their  ter- 
ritory is  slight,  so  that  it  would  hardly  be  safe  to  say 
that  they  are  not  dangerous  in  such  direction. 


FIG.  73. — Larva   and   pupa  of  buffalo 
gnat. 


RELATION  TO  OTHER  ANIMALS 


169 


The  Tabanidce,  including  those  forms  known  as 
"horse-flies,"  "deer-flies,"  "green-heads,"  "breeze-flies," 
"  golden -eyed  flies,  "  and  perhaps  a  number  of  other  pop- 
ular terms,  are  all  much  larger  species,  some  of  them 
among  the  largest  in  the  order.  They  are  all  blood 
suckers  in  the  female  and  feeders  on  nectar  or  other 
plant  secretions  in  the  male.  In  fact  the  males  are 
as  shy  and  retiring  as  the  females  are  bold  and  obtru- 


Fio.  74. — Black  horse-fly,  Tabanus  atratus:  a,  larva;   b,  pupa;  c,  adult. 


sive,  and  very  little  is  actually  known  of  them  and  their 
habits.  The  popular  names  are  all  applied  to  the  fe- 
males and  are  chiefly  based  on  their  habits  or  appear- 
ance. The  "horse-flies"  are  among  the  largest  of  the 
species — some  of  them  great  massive  fellows  an  inch 
or  more  in  length;  black,  blue,  brown  or  striped  with 
yellow;  sometimes  covered  with  a  bluish,  whitish  or 
golden  bloom.  They  attack  horses  or  cattle  in  their 
districts  and  so  stout  and  short  are  their  horny  lancets 
that  blood  comes  almost  as  they  settle.  High-strung, 
thin-skinned  horses  are  sometimes  driven  frantic  by 


i;o  INSECTS 

the  bites  and  by  the  circling  of  the  flies  seeking  a  place 
to  alight,  and  high-bred  cattle  fall  off  seriously  in  fly- 
infested  pastures. 

I  have  referred  to  districts  in  connection  with  these 
flies  and  not  unintentionally,  because  they  are  by  no 
means  generally  distributed.  Each  species  has  its 
favorite  haunt  and  cannot  be  found  outside  of  it;  so, 
in  driving,  one  may  enter  a  fly  district  and  get  out  of  it 
again  in  a  few  minutes.  Or,  after  being  bothered  for 
a  few  minutes  by  a  large  black  fly,  it  may  be  noticed 
that  a  large  brown  or  striped  one  has  taken  its  place. 

The  "green-heads"  are  usually  found  along  the 
sea-shore  and  their  name  is  due  to  the  bright  green  eyes 
which  cover  so  much  of  the  head  that  nothing  else  is 
ordinarily  noticed.  The  rest  of  the  body  is  generally 
of  some  light  or  yellowish  shade  that  is  inconspicuous  in 
the  surroundings  in  which  they  occur. 

The  "golden-eyes,"  "deer-"  or  "breeze-"  flies  are 
usually  inhabitants  of  damp  woods  and  their  names 
are  derived  partly  from  the  golden  brown  mottled  eyes, 
partly  from  their  supposed  habit  and  partly  from  their 
manner  of  attack.  These  are,  as  a  rule,  smaller  flies 
and  many  of  them  have  the  wings  barred  or  mottled 
with  brown  or  black.  The  golden  markings  of  the  eyes 
are  quite  conspicuous,  and  it  has  been  interestingly 
demonstrated  that  this  is  due  to  a  distinct  pattern  for 
each  species  and  that  in  life  many  forms  are  identifiable 
by  this  character  alone. 

The  Tabanid  larvae  so  far  as  we  know  them,  live  in 
mud  or  at  least  in  moist  earth  along  the  banks  of  streams 
or  almost  in  water  itself;  and  they  feed  on  the  minute 
forms  of  life  inhabiting  such  places.  Some  occur  on 
salt  marshes,  some  in  low  meadows  and  some  in  the 
damp  leaf  mould  in  low  woods,  and  this,  in  a  measure, 
accounts  for  the  local  distribution  of  the  adults:  they 


RELATION  TO  OTHER  ANIMALS          171 

do  not  get  very  far  away  from  the  place  where  they 
normally  breed. 

As  a  protection  against  these  insects  nettings  are 
used  on  driving  horses,  and  cattle  are  sometimes  pro- 
tected by  smears  of  carbolated  grease  or  fish  oil.  The 
larger  horse-flies  do  not  usually  attack  man,  as  the 
green-heads  and  deer-flies  generally  do.  Where  they 
are  abundant  enough  to  cause  trouble,  the  same 
repellants  that  serve  for  black  flies  will  serve  against 
the  Tabanids  as  well,  As  the  ground  becomes  better 
drained  or  cleared,  so  that  breeding  places  for  the  larvae 
are  lessened  in  number,  the  adults  will  become  gradually 
less  troublesome;  and,  as  a  matter  of  fact,  while  the  in- 
sects are  sometimes  horribly  annoying,  they  are  usually 
much  fewer  than  they  seem  because  of  their  active 
movements,  and  it  may  be  quite  possible  to  exterminate 
some  of  the  species  locally,  by  persistent  collecting  on 
some  especially  favored  animal,  for  a  few  days  after 
the  flies  first  make  their  appearance. 

The  term  "stable  flies"  is  rather  an  indefinite  one, 
but  applies  chiefly  to  one  species,  Stomoxys  calcilrans, 
of  very  general  distribution,  in  appearance  like  a  large 
house  fly,  but  with  mouth  parts  produced  so  as  to  be 
capable  of  sucking  blood.  These  are  often  present  on 
horses  and  cattle  in  great  numbers,  and  frequently 
cause  great  annoyance  and  distress.  They  rarely  attack 
humans,-  but  sometimes  in  hot,  oppressive  weather 
will  get  at  exposed  ankles  and  bite  hard,  usually  with- 
out causing  any  noticeable  swelling.  The  larvae  are 
maggots,  like  those  of  the  common  house  fly,  and  de- 
velop in  excrement,  preferably  in  cow  dung.  If  no  better 
lodging  is  found  for  them,  almost  any  kind  of  decaying 
vegetable  matter  will  be  made  to  answer. 

A  near  ally  to  this  stable  fly  is  a  somewhat  smaller 
species  known  as  the  "horn  fly"  from  its  habit  of 


172 


INSECTS 


clustering  at  the  base  of  the  horns  of  cattle.  This  is 
an  importation  of  comparatively  recent  date  from 
Mediterranean  Europe,  but  it  has  spread  in  the  few 
years  since  its  arrival  throughout  most  of  the  United 
States  and  into  Canada.  For  a  few  years  after  its 
first  appearance  it  produced  great  alarm,  and  weird 
stories  were  told  of  its  destructive  effect  on  cattle; 
the  least  of  which  was  that  the  flies  attacked  the  horns 


FIG.  75. — Horn  fly:  a,  egg;  b,  adult;  c,  d,  head  and  mouth  parts. 

at  base,  laid  their  eggs  there,  ate  off  the  root  of  the 
horn  and  then  penetrated  the  brain.  As  a  matter  of 
fact  much  injury  was  caused  to  dairies  from  the  abund- 
ance of  the  flies,  because  they  kept  the  cattle  in  a  con- 
stant state  of  irritation  and  therefore  poor  in  milk  flow. 
But  breeding  was  always  in  fresh  cow  manure,  and  at 
no  time  did  the  insects  get  within  the  outer  surface  of 
the  animal  in  any  stage.  After  two  or  three  years  of 
alarm  it  was  noticed  that  the  flies  lessened  in  number, 
and  finally  became  less  abundant  than  the  native 
species,  which  it  seemed  at  first  fated  to  displace. 


RELATION  TO  OTHER  ANIMALS  173 

Carbolated  fish  or  a  similar  oil  is  used  as  a  repellant, 
where  flies  of  this  character  are  abundant;  but  proper 
attention  to  the  manure  so  as  to  prevent  breeding  is 
a  much  more  effective  and  satisfactory  measure. 

Leading  to  those  species  that  have  been  referred 
to  as  parasitic  because,  in  the  larval  stage,  they  are 
confined  to  and  dependent  on  the  host,  are  a  number  of 
species  that  in  a  sense  are  intermediate  in  habit.  There 


FIG.  76. — Screw-worm,  Lucilia  macellaria:    a,  b,  c,  larva  and  details;    d, 
pupa,  e,  fly;  /,  its  head. 

are  many  species  that  are  true  scavengers  in  the  larval 
stage;  maggots  which  are  found  on  exposed  meats, 
fish  or  vegetable  matter,  and  which  in  an  almost  in- 
credibly short  time  dispose  of  most  of  the  organic  matter 
of  an  animal  of  even  considerable  size.  And  in  the 
determination  of  what  is  suitable  organic  matter,  the 
adult  flies  of  some  species  seem  to  follow  the  rule 
that  it  is  best  to  "blow"  anything  that  might  by  any 
chance  be  suitable.  Hence  while  the  parent  of  the 
" screw- worm"  normally  lays  her  eggs  in  or  on  dead 
animals  or  on  exposed  meats,  yet  sometimes,  when 
suitable  food  is  scarce,  she  will  select  any  raw  or  sore 


174  INSECTS 

surface  on  even  a  living  animal.  Most  of  the  flies  of 
this  series  are  attracted  by  foul  odors  which,  to  them, 
is  an  indication  of  a  suitable  place  for  eggs;  hence  it 
is  not  altogether  unusual  to  have  a  female  oviposit 
into  the  open  mouth  or  into  the  nostrils  of  a  sleeping 
human  afflicted  with  catarrh  or  some  other  trouble 
giving  rise  to  foul  breath.  Eggs  of  this  kind  are  usually 
ready  to  hatch  .when  laid  and  sometimes  already  hatched 
within  the  abdomen  of  the  female;  hence  it  is  a  matter 
of  only  a  very  short  time  for  the  young  larva  to  make 
its  way  along  the  mucous  membrane,  in  which  it  may 
exist  for  a  day  or  two  without  giving  rise  to  much  dis- 
comfort. After  this  it  bores  into  the  soft  tissue  of  the 
palate  and  into  the  cavities  and  sinuses  of  the  head, 
giving  rise  to  intense  pain,  high  fever  and  often  death, 
if  the  character  of  the  trouble  has  not  been  at  once 
recognized  and  prompt  treatment  made.  Yet  this 
form  of  parasitism  is  incidental  or  accidental,  and  shows 
principally  how  slight  and  easy  is  the  step  from  the 
beneficial  scavenger  to  the  injurious  parasite.  When 
the  eggs  are  deposited  on  or  near  an  open  wound  or 
sore  surface,  the  larvae  bore  into  the  exposed  tissue  and 
feed  upon  the  living  flesh,  which  of  course  becomes 
much  inflamed,  ulcerates  and  attracts  yet  other  flies 
of  the  same  character,  unless  the  matter  is  promptly 
looked  after.  The  screw-worm  flies  are  common  enough 
throughout  the  middle,  southern  and  central  states, 
but  are  most  troublesome  in  the  south  and  the  south- 
west where,  during  some  years,  much  loss  among  domes- 
tic animals  has  resulted  from  their  attacks.  The  adults 
are  stout  flies  almost  two-fifths  of  an  inch  long, 
metallic  bluish  in  color,  with  three  blackish  longitudinal 
stripes  on  the  upper  side  of  the  thorax. 

A  very  similar  but  somewhat  smaller  species  is  the 
blue-bottle  fly,   much  more  common  in  the  northern 


RELATION  TO  OTHER  ANIMALS          175 

states  and  more  metallic  yellow  or  green  in  color,  which 
has  similar  habits  so  far  as  attacking  wounds  or  raw 
surfaces  is  concerned;  but  it  does  not,  so  far  as  I  am 
aware,  ever  actually  bore  into  living  flesh  nor  into  the 
openings  of  the  face.  The  nearest  approach  to  this 
was  in  the  case  of  a  tramp  admitted  to  the  hospital  at 
New  Brunswick,  complaining  of  unbearable  headache. 
Investigation  showed  the  ear  cavities  rilled  with  a  dirty 


FIG.  77. — Blue- bottle  fly,  Lucilia  casar. 

mass  in  which  were  found  maggots  which  I  believe 
were  of  this  species.  The  ears  were  cleaned,  syringed 
and  all  the  maggots  removed  before  they  had  pene- 
trated further  into  the  head  cavities. 

The  large  blue  "meat-fly"  or  "blow-fly"  has  sim- 
ilar habits  and  seems  to  occur  all  over  the  world,  at- 
tracting attention  by  its  large  size,  deep  blue  color 
and  noisy  hum. 

The  one  guard  against  all  these  semiparasitic  scav- 
engers is  cleanliness  and  disinfection.  It  is  the  attrac- 
tion of  foulness  that  brings  them  to  the  attack,  and  if 
by  unavoidable  accident  an  attack  is  made  on  some 


i76 


INSECTS 


unprotected  point,  prompt  treatment  to  destroy  the 
larvae,  reduce  inflammation  and  protect  the  wound, 
should  be  resorted  to.  Carbolated  washes  or  ointments 
are  excellent  as  protectives,  and  nothing  is  better  than 
peroxide  of  hydrogen  to  clean  and  sterilize  a  suppur- 
ating sore. 

It  is  rather  an  easy  step  from  the  sort  of  elementary 
parasitism  just  described,  to  the  simpler  forms  of  at- 
tack by  bot-flies,  or  (Estrida.  Bot-flies  in  the  adult 
stage  are  usually  large,  stout  species  with  a  large  head, 
but  no  functional  mouth  parts. 
The  adults,  therefore,  though 
very  highly  specialized  in  some 
directions,  are  merely  produced 
to  provide  for  the  continuance 
of  the  species ;  incapable  of  harm 
in  themselves  and,  so  far  as  we 
know,  not  productive  of  any 
distinct  good. 

In  the  simplest  forms  the 
adult  fly  lays  an  egg  on  the  skin 
of  the  animal  that  serves  as  a 

host;  the  larva  hatches,  bores  its  way  through  the  skin, 
enters  the  tissue  and  lodges.  It  increases  in  size,  some- 
times forms  a  swelling  which  may  or  may  not  suppurate, 
and,  when  full  grown,  works  out  through  the  skin,  drops 
to  the  ground  which  it  enters  to  pupate,  develops  to  an 
adult  in  due  course  and  the  cycle  is  complete.  Bots  of 
this  character  attack  a  great  variety  of  animals  and  even 
man  is  not  exempt  from  them.  I  have  personal  knowl- 
edge of  such  a  case  and  there  are  enough  others  on 
record  to  make  it  quite  certain  that  under  abnormal 
conditions  some  of  the  species  that  ordinarily  attack 
other  animals  may  attack  man.  In  tropical  regions  the 
attacks  on  man  are  much  more  frequent  and  are  referred 


FIG.  78. — Blow-fly,  Calliphora 
vomitoria. 


RELATION  TO  OTHER  ANIMALS 


177 


to  species  of  Dermatobia.  So  far  as  I  am  aware  no 
species  has  been  demonstrated  that  is  confined  to 
human  beings. 

Almost  any  part  of  the  animal  body  may  be  at- 
tacked by  bots;  but  in  a  general  way  they  are  most 
likely  to  appear  in  regions  which  the  host  is  least  able 
to  reach  with  its  teeth,  e.g.,  the  neck;  but  they  occur 
often  enough  in  other  portions  of  the  body.  Occa- 


FIG.  79. — The  sheep  hot,  CEstrus  ovis:   i,  2,  flies;  3,  pupa;   4,  5,  full-grown 
larvae;  6,  young  larva. 


sionally  they  appear  to  attack  specific  organs  as  those 
that  destroy  the  testes  of  squirrels  and  chipmunks,  or  to 
be  confined  to  special  regions  like  those  that  are  so  often 
found  around  the  anal  openings  of  hares  and  rabbits. 

Some  species  have  almost  identically  the  habits  that 
were  observed  in  the  screw-worms  entering  the  head 
of  man  through  the  nostrils.  An  example  of  this  is 
the  well-known  sheep  bot,  the  adult  of  which  lays  its 
eggs  ready  to  hatch  or  just  hatched  on  the  mucus  of 
the  nostrils  of  the  sheep.  The  larvae  work  their  way  up 
into  the  head  passages,  feeding  on  the  mucus,  on  the 

12 


1 78  INSECTS 

membrane  itself  and,  if  pressed  for  food,  upon  the 
muscular  tissue.  When  the  infestation  is  a  bad  one 
they  work  their  way,  through  all  the  openings  between 
or  in  the  bones,  to  all  parts  of  the  head  cavity,  and  into 
the  brain  itself,  in  such  cases  causing  "staggers"  and 
death.  The  larvae  like  almost  all  bots  are  set  with 
short  stiff  spines,  definitely  arranged,  that  enable  them 
to  make  their  way  forward,  and  there  is  also  a  pair  of 
mouth  hooks  that  enables  the  grub  to  fasten  itself 
firmly  to  any  place  selected.  This  spiny  structure  and 
the  definite  mouth  hooks  are  not  developed  in  the 
"screw- worm,"  which  is  a  typical  maggot,  altogether 
unlike  the  highly  developed  "bot. "  The  amount  of 
damage  caused  by  the  sheep  bot  is  very  great  in  many 
localities,  while  in  others  the  species  seems  to  be  alto- 
gether unknown.  As  to  remedies  against  them,  each 
locality  or  herdsman  has  its  or  his  own,  and  none  is 
entirely  satisfactory. 

An  altogether  different  type  of  bot  is  that  which 
occurs  in  horses.  The  fly  that  produces  this  has  rather 
a  conical  pointed  abdomen  and  a  brown  hairy  body. 
The  eggs  are  laid  on  and  attached  to  the  hair,  usually 
on  the  forelegs  or  on  some  part  easily  reached  by  the 
horse  with  its  head;  and  they  remain  there,  unhatched, 
although  the  embryo  may  be  fully  developed,  until 
the  horse  in  licking  itself  or  a  companion  dislodges 
the  egg-cap  and,  freeing  the  larva,  transfers  it  to  the 
mucous  membrane  of  the  mouth.  From  this  place  it 
moves  at  once  and  makes  its  way  down  the  oesophagus 
into  the  stomach.  Here  the  young  bot  finds  its  proper 
conditions  and  becomes  anchored  by  means  of  a  pair 
of  mouth  hooks  into  the  lining  membrane.  It  feeds 
here,  absorbing  the  juices  for  several  months,  maturing 
in  late  spring,  and  then  loosens  its  hold,  is  carried  into 
the  intestines  with  the  excrement  and  so  on  through 


RELATION  TO  OTHER  ANIMALS 


179 


the  anus.  When  it  reaches  the  ground  it  burrows  into 
it  at  once,  changes  to  a  pupa,  and  not  until  a  month 
thereafter  does  it  transform  into  an  adult  fly.  A  full 
year  is  thus  required  for  the  development  of  the  species, 
and  there  is  only  one  danger  season  for  infection — the 
period  during  July  and  August  when  the  flies  are  on 
the  wing. 


FIG.  80. — The  horse  bot,  Gastrophilus  equi:  a,  egg,  attached  to  hair;  b,  young; 
c,  full-grown  larva;   d,  adult  fly;   e,  hooks  of  larva. 

A  few  bots,  while  not  of  course  an  advantage,  will 
not  hurt  a  horse.  More  than  a  few  will  cause  trouble, 
in  proportion  to  the  amount  of  infestation.  There  is, 
naturally,  the  irritation  to  the  membrane  to  which  the 
insects  are  attached,  causing  digestive  derangement; 
there  is  also  the  positive  drain  upon  the  system  by  the 
feeding  maggot  which  is  apt  to  weaken  the  animal  and 
to  intensify  the  effect  of  the  digestive  trouble;  and 
finally,  when  there  are  many  bots,  they  tend  to  form  a 
mechanical  obstruction  to  the  passage  of  food  from 


i8o  INSECTS 

the  stomach  to  the  intestine.  A  bad  infestation  is  a 
serious  matter  and  may  easily  become  fatal. 

On  well-cared-for  horses  bots  are  not  often  trouble- 
some. The  eggs  are  readily  seen  and  as  they  cannot 
be  hatched  for  several  days  after  being  deposited, 
they  may  be  easily  removed  when  the  animal  is  groomed. 
They  are  firmly  enough  attached,  however,  not  to 
be  easily  removable  by  the  horse,  and  the  embryo 
develops  within  ten  days  after  they  are  laid.  If  at  any 
time  after  that  the  egg  is  licked,  the  cap  covering  the 
top  opens  and  the  larva  slips  out  of  the  shell  on  to  the 
tongue,  moving  actively  at  once  toward  the  gullet. 
A  thorough  brushing  and  washing  once  every  week 
will  therefore  be  sufficient  to  keep  a  horse  free,  even 
when  exposed  to  the  attacks  of  the  flies. 

It  is  curious  to  note  how  all  animals  subject  to  bots 
appear  to  dread  the  adult  flies.  They  cannot  possibly 
know  the  relationship  between  the  flies  and  the  bots, 
and  it  is  probably  the  apparent  intention  to  attack 
that  arouses  the  fear  that  undoubtedly  exists. 

Horned  cattle  are  subject  to  the  attacks  of  bots 
that  form  swellings  or  "warbles"  under  the  skin, 
usually  on  each  side  of  the  backbone;  and  these  insects 
affect  not  only  the  general  health  of  the  animal,  but 
very  materially  reduce  the  value  of  its  hide.  In  fact 
the  impairment  of  value  so  caused  has  been  reckoned 
at  many  millions  annually  while  the  impairment  in 
value  of  dairy  products,  due  to  the  poor  condition  of 
suffering  cows,  can  hardly  be  estimated. 

The  life  cycle  of  this  species  is  also  interesting  and, 
in  a  way,  decidedly  more  complicated  than  that  of  any 
of  the  species  previously  referred  to.  The  adult  is  not 
so  unlike  that  of  the  horse  bot ;  a  little  more  compactly 
built,  with  a  shorter  abdomen  and  a  somewhat  banded 
appearance  in  black  and  whitish.  Like  its  ally  it  lays 


RELATION  TO  OTHER  ANIMALS 


181 


its  eggs  on  the  hair  of  the  animal  it  infests,  and  here 
also  further  development  is  dependent  upon  the  in- 
troduction of  the  young  larva  into  the  mouth.  But 
there  the  resemblance  ceases,  for  the  young  larva,  in- 
stead of  permitting  itself  to  be  carried  to  the  stomach, 
attaches  itself  to  the  walls  of  the  oesophagus  and  bores 
its  way  through  into  the  muscular  tissue,  continuing  on 
until  it  reaches  the  desired  position  beneath  the  skin. 


FIG.  81. — The  ox  bot,  Hypoderma  lineata:  a,  eggs  attached  to  hair; 
b,  fly;   c,  larva. 


As  with  the  horse,  the  well-cared-for  dairy  animal 
rarely  suffers  from  bots;  the  eggs  are  so  conspicuous 
that  they  readily  attract  attention,  and  removal  is 
easy.  If  any  do  escape  and  bot-swellings  are  noticed, 
they  should  be  lanced  and  the  contained  larva  removed. 
Cattle  on  the  range  or  beef  cattle  in  pasture  suffer  much 
more,  because  they  are  less  or  not  at  all  looked  after, 
and  the  bots  are  not  suspected  until  the  ulcerating 
sores  attract  attention. 

A  still  more  highly  specialized  type  is  represented 
by  the  "louse  flies,"  sometimes  separated  under  the 


182  INSECTS 

term  Pupipara,  or  those  that  give  birth  to  pupae.  They 
are  usually  active,  flattened,  brown  or  yellow  flies, 
with  small  head  and  rounded  abdomen.  Some  of  them, 
infesting  birds  of  prey,  fly  actively,  while  others,  like 
the  "sheep  tick,"  are  wingless,  although  not  there- 
fore inactive.  They  are  called  pupipara  because  the 
egg  hatches  within  the  body  of  the  female  and  the 
larva  attains  its  entire  growth  before  being  extruded, 
ready  to  pupate.  Of  course  this  means  a  very  slow 
rate  of  reproduction,  since  the  number  of  young  matured 


FIG.  82. — A  louse  fly,  Olfersia  species. 

at  one  time  cannot  be  great;  but,  on  the  other  hand, 
it  is  also  a  safe  rate,  because  the  larvae  run  few  dangers 
during  their  early  life,  and  the  infant  mortality  is  not 
very  high.  Nestlings  become  infested  from  the  mother 
bird,  and  the  flies  are  quite  active  enough  to  make 
short  flights  from  the  host  and  back  again  when  neces- 
sary to  escape  an  especially  vigorous  hunt.  When 
the  host  dies  or  is  killed  the  parasites  leave  it  at  once, 
and  seek  shelter  on  any  living  thing  in  the  vicinity. 
"Sheep  ticks"  which,  as  already  indicated,  are 
wingless,  do  really  look  very  much  more  like  ticks 
than  like  flies;  their  long  mouth  parts,  small  thorax, 
long  legs  and  round  flattened  abdomen  giving  them 


RELATION  TO  OTHER  ANIMALS  183 

a  peculiarly  spider-like  appearance.  They  are  some- 
times very  abundant  on  sheep,  and  find  no  difficulty 
in  getting  on  to  new  animals  because  of  the  habit  of 
congregating  into  dense  masses,  peculiar  to  their  host. 
The  body  of  these  flies  is  very  tough  and  leathery,  and 
I  am  informed  by  those  who  handle  the  raw  hides 
that  they  will  survive  all  the  preliminary  handlings, 
cleaning  and  soakings  which  the  pelts  undergo  before 
being  denuded  of  wool  and  prepared  for  tanning. 
Herders  know  of  a  great  variety  of  "dips"  useful 


FIG.  83. — Sheep  tick,  Melophagus  FIG.  84.  —  A    bat   tick, 

ovinus.  Nycteribia. 

against  these  insects  and  "dipping"  is  a  regular  prac- 
tice wherever  sheep  are  raised  in  any  numbers. 

The  extreme  development  in  this  direction  we  find 
in  the  bat  ticks,  which  are  even  more  spider-like  than 
the  sheep  tick  and  have  similar  habits,  while  infesting 
a  much-shorter-haired  animal.  It  is  distinctly  curious 
that  while  there  are  many  species  of  these  louse  flies 
among  birds,  there  are  only  a  few,  very  aberrant  forms, 
that  have  adapted  themselves  to  live  on  four-footed 
animals. 

We  find,  then,  that  among  the  insects  there  are  foes 
to  almost  all  kinds  of  vertebrates  and  that  they  are 
not  at  all  despicable  foes.  While  the  death  of  the 
animal  attacked  is  never  sought  as  a  prime  object, 


i84  INSECTS 

it  not  infrequently  follows  as  the  result,  and  it  is  not 
by  any  means  easy,  even  for  man  himself,  to  guard 
against  injury  in  all  cases. 

We  see  also  that  parasitism  is  not  by  any  means  a 
primitive  condition  but  an  adaptation,  frequently 
accompanied  by  specialization  of  a  high  order.  It  is, 
in  some  of  its  manifestations,  of  comparatively  recent 
origin,  the  greatest  diversities  obtaining  in  the  highly 
specialized  Diptera,  while  the  simple  forms  are  all 
in  the  more  generalized  orders,  being  there  little  more 
than  an  adaptation  to  life  on  an  animal  rather  than 
on  a  plant. 


CHAPTER  VIII 

THEIR  RELATION  TO  MAN  AS  BENEFACTORS 

INSECTS  as  benefactors  to  the  human  race  have 
been  very  little  considered,  their  position  on  the  op- 
posite side  having  been  so  much  more  emphasized ; 
and  yet,  if  some  few  species  were  eliminated,  their  ab- 
sence would  be  very  seriously  felt  for  a  time,  until  a 
substitute  for  them  could  be  discovered.  Possibly 
the  reference  to  them  as  benefactors  is  a  little  inac- 
curate for  most  of  those  referred  to  here — they  are 
useful  to  man  rather  than  his  benefactors.  We  might, 
of  course,  class  as  benefactors  those  that  pollenize  his 
fruits  and  other  crops;  but  there  the  benefit  is  indirect 
as  to  man,  and  more  direct  as  to  the  plants, hence  coming 
under  another  head. 

Directly  beneficial  to  man  are  those  insects  that 
act  as  scavengers,  working  to  reduce  to  their  original 
inorganic  compounds  those  animal  and  vegetable 
materials  that  are  dead  or  dying  and  of  no  further  use 
as  living  organisms.  The  extent  of  the  benefit  thus 
derived  is  absolutely  unappreciated;  but  were  all 
insect  scavengers  removed  at  one  time  and  all  dead 
animal  and  vegetable  material  left  to  other  decays, 
the  foulness  and  noxious  odors  that  would  be  thus  let 
loose  are  beyond  all  description. 

Does  a  small  animal  die  in  the  field — within  a  few 
hours  burying  beetles  are  working  to  get  it  under- 
ground; flies  have  laid  their  eggs  on  the  body  and 
numerous  other  species  have  begun  feeding  on  the  skin, 
the  hair  and  the  flesh.  Within  twenty-four  hours  in 
summer,  the  process  of  disintegration  is  well  under 

185 


1 86  INSECTS 

way  and  in  a  remarkably  short  time  nothing  but  the 
bony  framework  remains. 

Hardly  has  a  cow  dropped  a  mass  of  excrement 
in  the  pasture,  before  it  is  covered  with  flies  absorbing 
the  moisture,  helping  to  form  a  dry  outer  coating  and 
ovipositing  for  maggots  to  help  reduce  the  half-decayed 
mass  into  fragments  that  may  be  mingled  with  or  ab- 
sorbed by  the  soil.  If,  after  a  dropping  has  been  in 
the  field  forty-eight  hours,  it  is  broken  up  in  a  pail  of 
water,  the  number  of  specimens  and  species  that  will 
come  to  the  surface  is  startling. 

Is  a  forest  giant  stricken  and  borne  to  the  ground 
by  wind,  flood  or  lightning — immediately  insects  of 
many  sorts  attack  and  begin  to  reduce  it  to  dust,  con- 
tinuing their  work  until  nothing  remains.  And  so  of 
all  organic  matter  in  which  life  is  waning  or  from  which 
it  has  departed — such  matter  is  prey  to  insects  and  they 
are  never  backward  in  fulfilling  their  duty. 

This  scavenger  function  is  by  no  means  a  "low," 
or  "primitive"  habit;  it  does  not  exist  in  the  lowest 
orders  at  all  and  is  best  developed  in  the  Coleoptera 
and  Diptera,  which  are  among  the  highly  specialized 
and  dominant  types.  To  be  sure  the  Thysanura  are 
largely  feeders  on  the  products  of  decay  and  hence 
may  seem  to  be  entitled  to  rank  as  scavengers;  but 
they  rather  come  after  decay  and  feed  on  its  products, 
hence  their  presence  is  merely  indicative  of  moisture 
and  decay  produced  by  other  causes. 

The  Termites  among  the  Neuropterous  orders  are 
feeders  on  wood  and  other  vegetable  products,  but  they 
invade  rather  for  building  purposes  and  are  never 
found  in  really  decaying  material. 

The  order  Hemiptera  contains  no  scavengers  among 
either  the  Homoptera  or  Heteroptcra  and  stands  entirely 
free  from  even  a  tendency  in  that  direction. 


THEIR  RELATION  TO  MAN  187 

In  the  Coleoptera  or  beetles  there  are  several  families 
that  are  scavengers  in  whole  or  in  part,  and  some  of 
these  families  contain  very  large  numbers  of  species. 
In  a  very  general  way  the  scavengers  may  be  recog- 
nized by  the  clavate  or  club-shaped  antennae,  combined 
with  five- join  ted  feet  or  tarsi,  and  thus  belonging  to 
the  series  ll  Clavicornia.  " 

The  Stapkylinidos  or  rove-beetles  are  found  wherever 
decaying  or  fermenting  material  occurs,  although  by 
no  means  all  the  Staphylinids  are  scavengers.  They 
are  long,  slender,  somewhat  flattened  beetles,  with 
wing-covers  or  elytra  extending  over  only  two  segments 
of  the  abdomen.  The  other  segments  are  free  and 
flexible,  often  readily  up-curved  so  that  it  sometimes 
appears  as  if  they  intended  to  sting.  Some  of  these 
species  are  so  small  and  slender  that  they  are  difficult 
to  see  and  some  are  of  considerable  size;  sometimes 
they  are  smooth  and  shining  and  sometimes  densely 
covered  with  short  silky  pile,  both  methods  serving 
to  keep  the  insects  clean  in  their  often  unsavory  sur- 
roundings. As  an  indication  of  their  habits  some  of  the 
species  have  peculiarly  sickening  odors  that  in  penetra- 
tion and  volume  are  altogether  out  of  proportion  to  the 
size  of  the  insect  producing  them.  In  animal  or  vegeta- 
ble decay,  in  excrement,  under  and  in  dead  animals,  in 
the  fermenting  sap  of  injured  or  dying  trees,  in  fungi  of 
all  kinds — in  all  these  places  our  Staphylinids  occur  and 
everywhere  do  their  share  of  the  needed  work. 

Closely  allied  to  them  come  several  families  of 
minute  beetles,  some  of  them  of  odd  and  bizarre  shapes; 
all  of  them  with  the  enlargement  or  club  of  the  antenna 
well  marked,  and  all  of  them  feeders  on  dead  or  decay- 
ing matter.  Their  names  alone  would  tell  us  nothing; 
to  go  into  their  habits  and  peculiarities  would  require 
another  book,  for  there  are  literally  hundreds  of  them. 


i88 


INSECTS 


Conspicuous  in  appearance  and  habit  are  the  bury- 
ing beetles  and  carrion  beetles,  their  names  indicative 
of  their  functions.  They  are  often  of  moderate  or  large 
size  and  at  the  end  of  the  feelers  the  club  is  capitate  or 
shaped  like  a  head,  an  arrangement  that  permits  the 
organization  of  an  extremely  sensitive  olfactory  system. 
The  sense  of  smell  in  these  insects  is  so  well  developed 
indeed,  that  even  a  small  dead  animal  is  unerringly 

located  very  soon  after  its 
demise.  I  have  seen  these 
beetles  climb  to  the  tip  of 
a  twig,  extend  the  antennae 
in  every  direction  with  the 
leaves  of  the  tip  widely  sep- 
arated, and  then  fly  in  a 
straight  line  and  without  hes- 
itation in  the  direction  from 
which,  apparently,  an  agree- 
able odor  was  perceived.  The 
burying  beetles  are  so  called 
because  of  their  habit  of 
digging  out  the  soil  from 
beneath  a  small  animal  un- 
til it  sinks  down  to  or  below 

the  level  of  the  ground,  and  the  powerful  head,  thorax 
and  legs  are  well  adapted  for  this  kind  of  work.  The 
carrion  beetles  are  quite  as  prompt  in  their  arrival, 
but  do  not  work  in  the  same  way.  They  are  content 
with  ovipositing  on  or  under  the  cadaver,  trusting  the 
resulting  larvae  to  their  own  devices.  And  what  a  lot 
and  variety  of  these  carrion  beetles  there  are!  Species 
so  small  as  to  be  almost  invisible  to  the  unaided  eye, 
and  others  an  inch  or  more  in  length.  Species  smooth 
and  shining  so  that  none  of  the  material  in  which  they 
live  can  adhere  to  them,  and  species  covered  with  fine 


FIG.  85. — A  burying  beetle,  Necro 
phorus  americanus . 


THEIR  RELATION  TO  MAN  189 

silky  pubescence,  or  rough  and  ridged  for  the  lodgment 
of  any  sort  of  material,  serving  in  some  cases  to  disguise 
and  conceal.  And  as  with  most  of  the  scavenger  fam- 
ilies, not  all  of  the  species  are  confined  to  animal  foods. 
Some  are  found  in  decaying  vegetation,  and  yet  more 
in  fungi,  which  harbor  a  great  number  of  species. 

The  Histeridce  or  "pill  beetles"  are  little,  chunky 
creatures  shining  black  or  metallic  in  appearance,  and 
the  legs  all  broad  and  flattened,  fitted  for  digging. 
They  occur  in  decays  and  ferments  of  all  kinds,  but 
their  habits  are  more  diverse  than  in  some  of  the  other 
groups,  predatory  forms  being  not  uncommon. 

And  then  come  those  species  allied  to  the  Dermes- 
tid(B  or  larder  beetles;  species  that  feed  upon  dead 
organic  material  but  which  instead  of  being  advan- 
tageous are  rather  the  reverse,  since  they  often  feed 
upon  material  that  man  desires  for  his  own  use,  like 
dried  and  smoked  meats,  hides  and  even  the  animal 
fabrics.  Here  again  we  note  that  the  matter  of  use- 
fulness is  after  all  only  a  relative  one,  since  the  very 
function  that  makes  a  species  valuable  when  it  affects 
something  of  no  use  to  man,  makes  it  harmful  when  it 
affects  something  that  he  wishes  to  keep. 

There  are  exceptional  scavengers  in  most  of  the 
other  beetle  families,  but  none  that  need  mention 
here  except  the  "tumble-bugs"  and  their  allies,  which 
feed  on  excrementitious  material,  often  rolling  large 
balls  of  dung  from  the  place  where  it  was  found  to  a 
place  where  it  can  be  conveniently  buried  to  serve  as 
food  for  their  larvae.  These  tumble-bugs  are  members 
of  the  Lamellicorn  series  which  contains  mostly  plant 
feeders  and  which  are  more  fully  referred  to  as  plant 
enemies. 

The  Lepidoptera  contain  no  scavengers  strictly 
speaking,  although  there  are  some  species  that  feed 


1 9o  INSECTS 

on  dried  organic  matter,  animal  as  well  as  vegetable, 
and  in  the  Hymenoptera  only  the  ants  may  be  classed 
as  such.  Ants,  of  course,  are  feeders  on  a  very  great 
variety  of  materials.  Some  species  will  attack  and 
devour  any  living  thing  that  comes  in  their  way ;  others 


FIG.  86. — A  "tumble-bug,"  Copris  Carolina:  a,  larva;   b,  the  cell  in  which 
it  lived;  c,  pupa;  d,  female  beetle. 


confine  themselves  to  vegetable  food  only  and  yet 
others  seem  to  be  restricted  to  liquid  food.  Most  of 
them  have  quite  a  range  of  supplies  and  some  species 
may  be  found  almost  anywhere,  even  in  our  houses. 
And  yet  ants  are  rarely  thought  of  as  real  scavengers, 
for  they  are  not  seen  in  or  on  decaying  animals  or  in 
or  on  foul  excrements. 

In   the   Diptera,   however,   we   have    scavengers   in 
great  number  and  variety;    and  yet  very  much  alike 


THEIR  RELATION  TO  MAN 


191 


after  all,  for  in  the  larval  stage  they  are  nearly  all  mag- 
gots, similar  to  those  of  the  common  house  fly.  -Wher- 
ever an  animal  dies,  a  mass  of  excrement  drops  in  the 
field,  an  over-ripe  fruit  falls  to  the  ground  or  a  pail  of 
garbage  is  set  outdoors,  there  we  find  flies  present  at 
once  and  in  a  few  hours  young  maggots.  It  has  been 
said  that  flies  will  devour  an  ox  more  rapidly  than  a  lion 
and  while  that  may  be  a  little  exaggerated,  they  will 
certainly  make  a  more  complete  job  of  it.  It  is  literally 


FIG.  87. — Pommace  fly;  Drosophila  ampelophila:  a,  adult;   b,  larva; 
d,  e,  pupa. 

astounding  to  note  how  rapidly  a  small  carcass  may  be 
transformed  into  a  mass  of  squirming  maggots,  ap- 
parently liquefying  the  tissues  so  that  they  may  be  ab- 
sorbed through  the  small  mouth  orifice.  And  it  needs 
so  little  to  attract  these  flies.  Lay  out  a  few  bruised 
apples,  pears  or  other  fruit  on  a  table,  and  in  a  short 
time  they  will  be  covered  with  little  yellowish  or  gray 
flies  having  bright,  brick-red  eyes — pommace  flies — 
coming  from  no  one  knows  where,  but  attracted  by  the 
odor  of  the  ferment.  In  the  fall  when  cider  or  wine  is 
making,  every  tub  or  barrel  of  must  is  an  attraction, 
and  in  the  ferment  thrown  out  of  the  bung  of  the  wine 
cask  the  larvae  occur  by  the  hundred.  Not  long  as 


192  INSECTS 

larvas  either,  for  in  two  or  three  days  they  have  become 
full-grown,  change  to  a  pupa  and  then  to  the  adult 
condition.  And  so  we  find  that  in  this,  the  most  highly 
organized  series  of  insects,  scavengers  are  numerous  and 
effective.  So  effective,  indeed,  that  their  usefulness  is 
not  recognized  by  the  average  man,  because  he  has  no 
chance  of  knowing  what  conditions  would  otherwise  be. 

Among  the  insects  of  direct  use  to  man  none  are  of 
greater  importance  than  the  silk-worms.  Silk  is  in 
such  general,  almost  universal,  use,  that  there  is  scarcely 
a  moderately  well-dressed  individual  of  either  sex 
that  does  not  have  some  of  it  as  part  of  a  garment 
or  other  article  of  wear.  Of  the  millions  who  wear  or 
use  silk  how  many  ever  know,  or  knowing,  realize,  that 
every  particle  of  that  silk  is  the  product  of  a  cater- 
pillar; nothing  more  than  a  dried  viscid  salivary  secre- 
tion, originally  intended  by  nature  as  a  covering  to 
protect  the  pupal  stage  of  the  insect?  This  covering 
or  case  is  called  a  cocoon,  and  cocoons  are  spun  by 
many  caterpillars,  some  of  them  much  larger  than  the 
Chinese  silk- worm. 

Why,  then,  if  there  are  many  silk  spinners  do  we 
use  one  only,  and  what  particular  advantage  has  the  silk 
of  this  species  over  all  others?  As  to  the  latter,  it  has 
few  advantages  over  other  caterpillar  silks:  it  is  not 
nearly  so  strong  as  some  produced  by  other  varieties, 
it  is  not  more  lustrous,  and  it  is  not  nearly  so  great  in 
quantity.  Its  one  great  advantage  for  our  use  is  that 
it  can  be  more  easily  reeled  than  any  other  known 
variety.  The  silk- worm,  when  ready  to  make  its  cocoon, 
spins  a  small  quantity  of  loose,  supporting  threads  or 
floss  and  then  starts  inside  this  framework,  spinning 
with  a  continuous  thread,  unless  interrupted,  until 
the  entire  cocoon  is  completed — a  thread  almost  a  mile 
long  which,  under  favorable  conditions,  can  be  unwound 


THEIR  RELATION  TO  MAN  193 

in  the  same  way  and  without  a  break!  Generally, 
other  caterpillars  that  spin  cocoons  do  not  work  con- 
tinuously; or  if  they  do  work  steadily  on,  they  make 
a  patchwork  affair  of  it.  They  may  spin  a  few  yards 
at  one  end,  break  the  thread,  put  in  a  few  yards  at  an- 


\ 


FIG.  88. — Silk-worm,  cocoon  and  male  moth. 


other  point,  and  so  on  until  the  work  is  completed, 
making  a  nice  even  job  when  everything  is  done,  but 
a  cocoon  that  cannot  be  profitably  unwound  or  reeled 
because  of  the  great  number  of  breaks. 

Then,    too,    the    particular   species,    Sericaria   mori, 

has  been  domesticated  so  long  that  it  has  developed 

some  highly  desirable  qualities.     The  adult  moths  are 

very  sluggish,  even  the  males  flying  little  or  not  at  all, 

13 


i94  INSECTS 

while  the  females  are  practically  incapable  of  flight. 
They  pair  readily  in  confinement,  are  hardy,  and  very 
fecund,  the  female  producing  several  hundred  eggs. 
All  these  advantages,  together  with  the  ease  of  handling 
the  caterpillars,  are  matters  in  favor  of  the  mori,  and 
its  propagation  is  largely  the  work  of  women  and 
children  who  do  it  as  a  side  issue  and  hence  very  cheap- 
ly. It  is  this  latter  factor  indeed  that  has  barred  silk 
culture  in  America,  where  the  cost  of  labor  is  too  high 
to  make  the  venture  attractive  to  any  class. 

It  has  already  been  said  that  the  silk  is  in  the  nature 
of   a  salivary  secretion;    but  that  is   only  partly  true, 


^^(/g^J/3^>~ 
Secreting  Glands 

FIG.  89. — Salivary  gland  of  silk-worm. 

because,  although  the  material  is  secreted  by  one  pair 
of  what  are  usually  salivary  glands,  these  glands  have 
been  so  enormously  enlarged  that  they  extend  along 
the  sides  of  the  body  for  almost  the  full  length  of  the 
caterpillar,  and  the  material  has  become  so  sticky  and 
viscid  that  it  could  not  possibly  have  any  digestive 
function.  The  two  glands  unite  into  a  single  outlet 
on  the  lower  lip  of  the  caterpillar,  and  as  soon  as  the 
fine  thread  of  liquid  issues  from  the  opening  of  the 
spinning  organ  and  comes  into  contact  with  the  air, 
it  hardens  sufficiently  to  hold  its  form,  reaching  its 
full  strength  and  elasticity  a  few  moments  later.  As 
to  the  value  of  silk  products  each  year,  they  must  be 
figured  in  millions  of  dollars,  so  that  the  humble  cater- 


THEIR  RELATION  TO  MAN  195 

pillar  adds  not  a  little  to  the  wealth  of  the  producing 
countries,  and  to  the  support  of  those  engaged  in  textile 
industries.  The  elimination  of  the  silk-worm  and  its 
product,  while  it  would  not  eventually  cause  mankind  any 
serious  inconvenience,  would  deprive  it,  for  all  time,  of 
one  of  its  most  valued  and  widely  employed  fabrics. 

Next  in  order  of  value  are  the  bees  and  bee-products 
which  seem  to  have  been  recognized  and  employed 
almost  or  quite  as  long  as  we  have  any  historic  records. 
Honey  from  wild  bees  is  known  to  every  savage  nation 
and  has  formed  an  important  item  of  food.  And  not 
of  food  alone,  for  away  back  in  the  dark  ages  it  was 
found  that  it  made  an  excellent  drink  when  fermented, 
the  "meth"  of  the  ancient  Saxons  being  the  ancestor 
of  the  "metheglin"  of  more  recent  times.  The  latter 
drink  is  little  known  now-a-days,  especially  in  cities  and 
towns  where  malted  and  distilled  liquors  are  in  use; 
but  it  has  still  a  vogue  in  a  few  sections  of  the  country, 
where  those  who  first  make  its  acquaintance  gain  a 
wholesome  respect  for  those  ancestors  of  ours  whose 
capacity  for  it  was  measured  by  "flagons,"  or  "horns." 

Wax  and  honey  as  products  of  the  bee  are  uni- 
versally known  and  the  organization  of  the  beehive  is  so 
well  understood  that  it  need  only  be  referred  to.  Paraf- 
fine  has  largely  supplanted  beeswax  for  many  purposes, 
while  sugar  and  glucose  have  replaced  honey ;  so,  even 
were  the  bee  now  completely  eliminated  from  our  fauna, 
mankind  would  still  worry  along.  Nevertheless,  bee- 
products  are  on  the  increase  rather  than  otherwise  and 
there  is  no  lessening  in  the  demand  for  them. 

The  products  of  the  "lac"  insects  known  as  "stick 
lac,"  "shell-lac,"  etc.,  are  yet  of  considerable  impor- 
tance although  the  insect  "lac"  has  now  been  largely 
replaced  by  cheaper  preparations  from  other  sources, 
for  general  use.  The  lac  insect  is  really  one  of  the  "soft 


196  INSECTS 

scales,"  allied  to  the  most  serious  of  our  tree  pests: 
indeed  it  is  a  tree  pest,  tolerated  only  because  the  insect 
is  of  more  value  to  us  than  the  plant  upon  which  it 
feeds.  Infested  twigs  are  cut  and  stored  when  the  insect 
has  reached  the  proper  stage,  and  the  adherent  scales 
and  their  secretions  are  dissolved  off  when  they  are  to  be 
commercially  used.  Lac  is  a  product  of  the  Orient  and 
many  of  the  fine  polishes  and  lacquers  of  Indian,  Chinese 
and  Japanese  workmen  are  based  upon  it.  There  are 
allied  species  of  Coccidcz  occurring  in  tropical  America; 
but  none  that  have  been  made  commercially  useful. 

Cochineal  as  a  source  of  a  beautiful  crimson  and 
scarlet  is  well  known  and  is  also  a  scale  insect  or  Coccus, 
belonging  to  the  mealy-bug  series.  It  infests -certain 
kinds  of  cacti  and  is  cultivated  in  plantations  called 
"nopalries. "  It  is  the  source  of  the  coloring  matter 
known  as  crimson  lake,  and  is  a  native  of  Mexico  and 
Central  America.  Before  the  day  of  aniline  colors 
cochineal  was  extremely  valuable  and  important;  but 
at  present  the  complete  elimination  of  the  insect  would 
cause  little  if  any  inconvenience. 

It  is  noticeable  that,  except  in  the  case  of  silk,  we 
have  substitutes  for  practically  all  the  insect  products 
and  even  silk  has  been  artificially  produced,  i.e.,  a 
product  so  closely  resembling  it  as  to  be  called  artificial 
silk  has  been  made  that  could  be  developed  practically 
in  case  of  necessity. 

In  olden  days  insects  had  a  wider  use,  and  out  of 
a  plague  a  food  supply  was  sometimes  developed. 
"Locusts"  or  grasshoppers  as  articles  of  food  are  known 
among  barbarous  nations  of  many  countries  where 
the  insects  are  sufficiently  abundant.  The  Indians  of 
the  Rocky  Mountain  regions  in  America  and  the 
aborigines  of  Africa  were  equally  familiar  with  a  grass- 
hopper diet  and  with  the  methods  of  preparing  them. 


THEIR  RELATION  TO  MAN  197 

It  has  even  been  suggested  that  there  is  no  reason  why 
they  should  not  be  retained  on  our  modern  bills  of  fare, 
and  experiments  have  been  made  in  different  methods 
of  preparation.  Fried  they  are  said  to  have  a  sweet, 
nutty  flavor,  while  in  a  stew  with  milk  they  recall 
oysters.  It  must  be  confessed  that  no  very  great  en- 
thusiasm has  ever  been  developed  for  this  kind  of  diet, 
and  on  the  whole  the  use  of  grasshoppers  for  food  pur- 
poses is  distinctly  on  the  wane. 

In  South  America  a  species  of  water  bug  of  the  Corioca 
series  occurs  in  great  abundance  in  some  localities  and 
lays  its  eggs  in  large  numbers  on  the  surface  among  the 
sedges.  These  eggs  are  gathered,  dried  and  preserved  by 
the  natives,  who  mash  and  bake  them  into  a  cake  that 
is  much  appreciated.  Inasmuch  as  the  eggs  have  a  very 
decided  bed-buggy  odor,  it  would  require  considerable 
education  to  make  that  sort  of  omelet  popular. 

The  large  boring  larvse  of  Coleoptera  and  even  some 
Lepidoptera  are  not  unusual  articles  of  food  in  tropical 
countries,  and  ants  or  ant  larvae  and  pupae  have  also 
served  as  sources  of  food  supply  to  uncivilized  man; 
but  as  civilization  tends  to  eliminate  the  insects  in  its 
advance,  their  decreased  numbers  would  render  them 
less  available  as  sources  of  supply  even  were  better  or 
more  usual  articles  not  more  plentiful. 

Galls  as  sources  of  supply  for  tannic  acid  are  still 
gathered  in  some  localities,  and  some  forests  are  com- 
mercially profitable  as  gall  producers.  When  inks  were 
largely  dependent  upon  galls  for  their  black  color,  there 
was  a  greater  demand  for  them  than  now,  when  chem- 
istry supplies  other  if  not  better  sources  of  more  or  less 
permanent  black  stains. 

Insects  have  from  time  to  time  served  as  ingredients 
in  medicaments ;  but  very  few  are  so  used  at  the  present 
time.  Of  these  the  Cantharides  or  blister  beetles  are 


198  INSECTS 

best  known  and  yet  most  widely  employed.  In  the 
body  juices  there  is  secreted  an  extremely  irritating 
material  known  as  cantharidin  which,  when  applied 
to  the  skin,  produces  blisters  or,  taken  internally,  pro- 
duces inflammatory  conditions  of  the  genito-urinary 
system.  Most  of  the  blister  beetles  possess  this  prop- 
erty to  some  extent,  and  a  fresh  specimen  of  any  of 
the  common  American  species  crushed  upon  the  skin 
will  produce  blisters;  but  the  officinal  preparations 
are  obtained  from  a  European  species,  known  as  the 


FIG.  90. — Spanish  flies,  Lytta  vesicatoria, 

Spanish  fly,  Lytta  vesicatoria,  from  the  locality  whence 
most  of  the  specimens  come  and  from  its  vesicating 
properties.  These  beetles  come  in  great  swarms  when 
they  emerge  and  are  on  the  wing  for  a  few  days  only, 
during  which  period  the  entire  country  is  engaged  in 
gathering  them  in  sheets  on  which  they  are  killed  and 
dried,  after  which  they  may  be  preserved  indefinitely. 
The  blistering  property  is  dissolved  out  of  the  powdered 
beetles  with  alcohol. 

Broadly  stated  there  are  no  insects  that  are  indis- 
pensable to  man;  there  are  a  few  that  are  very  use- 
ful to  him,  aside  from  those  that  are  plant  pollinators, 
and  he  makes  use  of  a  few  others  for  which  he  has 
substitute  materials  at  hand  and  already  in  partial  use. 


CHAPTER  IX 

THEIR  RELATION  TO  MAN:    AS  CARRIERS 
OF  DISEASES 

SINCE  the  development  and  general  acceptance  of 
the  microbian  or  "germ"  theory  as  applied  to  many 
contagious  and  infectious  diseases,  and  its  absolute 
demonstration  in  plagues  like  cholera,  typhoid  fever, 
dysentery  and  other  enteric  or  intestinal  troubles,  as 
well  as  in  consumption,  pneumonia,  diphtheria  and  other 
affections  of  the  respiratory  organs,  the  question  of  the 
agencies  concerned  in  the  distribution  of  these  germs 
has  come  to  the  front. 

The  surgeon  has  long  known  that  suppurations  and 
pus-producing  inflammations  might  be  carried  from  one 
individual  to  another  by  almost  any  sort  of  carrier;  so 
when  he  operates,  he  sterilizes  his  instruments,  his 
hands,  the  cut  or  bruised  surfaces,  and  protects  the 
wounds  by  antiseptic  dressings.  That  flies  were  among 
the  agencies  for  spreading  suppurations  was  soon 
learned,  and  the  readiness  with  which  flies  gather  on 
sores  or  raw  surfaces  is  matter  of  common  observation. 
When  it  was  observed  that  flies  of  various  kinds  gathered 
with  as  much  readiness  on  fecal  or  excrementitious 
matters  as  on  food  products  in  the  kitchen,  and  were 
ready  to  change  their  diet  from  one  to  the  other  without 
much  provocation,  the  conclusion  that  they  might  inocu- 
late the  food  products  and  through  them  healthy  indi- 
viduals from  the  fecal  matter  was  not  a  difficult  one 
to  draw. 

In  the  cholera  epidemic  at  Hamburg  not  so  many 
years'  ago,  this  was  absolutely  demonstrated  as  to  that 

199 


20O 


INSECTS 


disease.  It  remained  for  the  United  States,  during  its 
war  with  Spain,  to  demonstrate  with  equal  positiveness 
that  typhoid  and  other  enteric  fevers  could  be  carried 
in  the  same  way.  More  soldiers  killed  by  common 
house  flies  than  by  Spanish  bullets,  is  the  unenviable 
record,  and  the  most  unsafe  places  for  our  soldiers  were 
the  fly-infested  home  camps  where  open  latrines  and 
near-by  mess  tents  furnished  ideal  conditions — for  the 
flies  and  the  diseases. 


FIG.  91. — The  house  fly,  Musca  domestica:  larva  with  details  at  right,  puparium 

at  left. 

While  flies  are  not  the  only  carriers  of  enteric  disease 
germs  and  these  do  not  actually  depend  upon  insects  as 
their  sole  means  of  spread,  yet  the  habits  and  structures 
of  flies  are  peculiarly  adapted  for  effective  service  of  this 
nature  and  they  are  correspondingly  dangerous.  No 
other  insects  live  in  such  close  communion  with  man,  and 
so  much  are  they  regarded  as  a  matter  of  course  that 
their  companionship  at  our  table  arouses  no  fear;  and 
such  is  their  persistence  that  they  gain  admittance  to 
the  palace  of  royalty,  as  well  as  the  hovel  of  the  peasant. 
They  breed  in  all  sorts  of  decaying  and  excrementitious 
matter,  in  garbage  pails  and  even  in  neglected  corners  of 


THEIR  RELATION  TO  MAN 


201 


cellar  or  store-room;  a  very  little  material  serving  to 
mature  a  large  number  of  specimens.  The  common 
house  fly,  Musca  domestica,  prefers  horse-manure  for  its 
development  and  is  most  numerous  in  the  vicinity  of 
stables.  The  eggs  are  laid  in  little  masses  by  the  adults, 


FIG.  92. — Foot  of  the  house  fly:   a,  the  last  tarsal  joint  and  claws;  b,  claws  and 
pulvilli;  c,  a  small  section  of  the  pulvillus,  showing  hooked  hairs. 


the  larvae  or  maggots  hatch  almost  at  once,  and  a  week 
later  these  are  full  grown  and  ready  to  transform. 

On  the  soles  of  their  feet  flies  have  pads  of  very  fine 
hair,  which  serve  excellently  as  gatherers  of  micro- 
organisms from  the  surfaces  over  which  they  travel,  and 
equally  well  as  distributors  on  others  over  which  they 
may  track  later.  This  point  has  been  proved  experi- 
mentally by  allowing  flies  to  walk  over  cholera  excre- 


202  INSECTS 

tions,  and  afterward  over  plates  of  prepared  gelatin. 
In  the  incubator,  every  footprint  developed  a  flourish- 
ing colony  of  virulent  cholera  germs. 

The  mouth  parts  of  flies  are  almost  equally  well 
adapted  for  similar  purposes.  At  the  end  of  the  fleshy 
lips  are  lobe-like  expansions  furnished  with  chitinous 
ridges  by  means  of  which  the  pasty  masses  of  food  are 
scraped  into  shape  to  be  ingested  by  the  insect.  These 


FIG.  93. — Lapping  organ  at  the  tip  of  the  fly  mouth. 

ridges  are  excellent  resting  places  for  the  minute  organ- 
isms and,  when  the  flies  change  their  diet,  the  germs  are 
directly  inoculated  into  the  new  food  material,  what- 
ever its  character.  And  flies  are  not  always  cleanly  in 
their  habits,  but  void  their  excrement  anywhere  in 
small,  pasty  masses  which  dry  quickly.  It  has  been 
shown  that  the  bacilli  of  intestinal  troubles  pass  through 
the  digestive  tract  of  the  insect  unchanged,  hence  every 
"fly  speck"  may  be  a  source  of  danger. 

This  method  of  transfer  for  pathogenic  organisms  is 
very  simple  and  direct,  and  is  applicable  only  to  forms 


THEIR  RELATION  TO  MAN  203 

that  undergo  no  change  and  which,  when  implanted  in 
a  suitable  medium,  will  continue  their  growth  and 
increase  with  unabated  virulence.  We  have  yet  quite  a 
different  class  of  diseases,  also  due  to  microscopic  or- 
ganisms, but  of  an  altogether  different  type:  minute, 
single  celled  animals  in  fact,  that  live  in  special  body-  or 
blood-cells,  but  are  not  capable  of  completing  their  en- 
tire life  cycle  in  a  single  host. 

The  best  known  example  of  this  sort  of  infestation  is 
that  due  to  the  Plasmodium  parasite  which  produces 
what  is  loosely  known  as  malaria.     It  is  not  so  long  ago 
that  almost  any  sort  of  indefinite 
illness  was  likely  to  be  classed  as  a 
"touch  of    malaria:"    now-a-days 
when    a    doctor    diagnoses    "mal- 
aria"   he    refers    to    an    affection 

FIG.  94.  —  Part   of    one 
Caused     by     One     Of     tWO     Or     three        of  the  pseudo-trachea  used 

specific  organisms  that  have  very      as  scraping  organ' 
definite    life    cycles    and    produce 

very  definite  results.  All  of  them  agree  in  being  Spor- 
ozoa,  i.e.,  animals  that  reproduce  by  means  of  spores,  and 
in  that  they  do  not  complete  their  entire  life  cycle  with- 
in the  body  of  their  human  host.  The  parasite  producing 
the  ordinary  type  of  tertian  malaria  or  "  chills  and  fever  " 
lives  in  the  red  blood-corpuscles  of  the  human  body  and 
comes  to  maturity  in  such  a  blood-cell  in  forty-eight 
hours.  It  then  breaks  up  into  a  mass  of  minute  spores 
which  rupture  the  cell  and  are  liberated  into  the  blood- 
serum.  In  this  they  float  about  for  a  short  time,  and 
then  each  spore  makes  its  way  into  a  sound  red  blood- 
corpuscle,  and  in  forty-eight  hours  is  itself  mature  and 
in  turn  reproduces  in  the  same  way.  As  all  the  parasites 
come  to  maturity  and  liberate  their  spores  at  about  the 
same  time,  this  causes  a  disturbance  of  the  body  tem- 
perature resulting  in  a  chill,  followed  by  a  fever  when  the 


204  INSECTS 

spores  are  entering  new  blood-corpuscles.  In  other  words 
the  "chills"  and  "fever"  merely  emphasize  the  period 
at  which  the  parasite  sporulates,  and  the  ill  effects  of 
malaria  are  due  to  the  gradual  destruction  of  the  red 
blood-cells. 

If  some  of  this  infested  blood  be  drawn  from  a  pa- 
tient and  injected  into  the  circulation  of  a  healthy  indi- 
vidual, a  new  case  of  malaria  will  result;  but  in  no  other 
way  can  there  be  a  direct  infection  from  one  individual 
to  another.  Normally  this  reproduction  by  means  of 
spores  continues  in  an  infested  individual  for  some  time 
and  then,  in  addition  to  the  spores,  special  cells  develop 
which,  when  liberated  into  the  blood-serum,  make  no 
attempt  to  enter  new  blood-corpuscles.  These  are  the 
"gametes,"  of  two  types,  differing  a  little  in  size  and 
form  and  termed  respectively  "micro-"  and  "macro- 
gametes.  "  They  undergo  no  change  in  the  human  body 
and  may  remain  in  that  stage  for  an  indefinite  period, 
even  when  the  active  reproduction  of  the  Plasmodia 
has  been  checked  and  the  patient  is  apparently  well. 
Taken  from  the  human  body  by  any  sort  of  blood- 
sucker or  even  drawn  on  a  properly  prepared  slide, 
further  development  takes  place.  From  the  micro- 
gametes  slender,  whip-like  processes  are  produced, 
known  as  "flagellae,"  and  these  break  off  and  represent 
the  male  element  that  unites  or  conjugates  with  the 
large  unaltered  "  macrogamete  "  representing  the  female 
element.  At  this  point  development  stops  unless  the 
blood  is  in  the -stomach  of  a  mosquito  belonging  to  the 
genus  Anopheles.  If  it  is  not  only  Anopheles,  but  a 
member  of  the  right  species,  the  conjugated  gamete 
elongates  and  becomes  a  "vermicule"  which  bores  into 
the  tissue  of  the  mosquito  stomach,  increases  in  size  and 
gradually  works  its  way  to  the  outer  surface  where  it 
forms  a  little  lump  or  protuberance,  now  known  as  a 


THEIR  RELATION  TO  MAN 


205 


"zygote."  In  about  ten  days  this  form  matures  and 
bursts,  liberating  thousands  of  "blasts"  or  "sporo- 
zoits"  into  the  body  cavity  of  the  mosquito.  In 


FIG.  95. — Anopheles  and  Malaria:  a,  larva;  b,  pupa;  c,  adult;  d,  the  blast 
introduced  into  the  blood  by  the  mosquito;  e  to  ;',  stages  through  which  the 
Plasmodium  passes  in  the  red  blood-corpuscle;  k,  the  spores  which  enter  new 
blood-corpuscles;  /,  m,  the  microgamete ;  n,  o,  the  macrogamete ;  p,  flagellae 
forming;  q,  union  of  a  flagellum  with  macrogamete;  r,  fusion  of  nuclei;  s,  the 
vermicule;  t  to  y,  formation  of  the  zygote  in  the  mosquito  stomach;  the  fully 
developed  zygote,  y,  rupturing  to  produce  blasts  d. 


206  INSECTS 

some  way  these  gather  into  the  salivary  glands,  and 
when  that  mosquito  bites  again,  it  introduces  with  its 
droplet  of  saliva  a  large  number  of  "sporozoits"  which, 
if  they  find  conditions  favorable,  enter  red  blood- 
corpuscles  and  set  up  a  case  of  malaria. 

The  transmission  of  this  disease,  then,  is  by  no  means 
a  simple  matter,  and  the  proper  species  of  Anopheles  is 
absolutely  essential  to  it.  The  elimination  of  these  mos- 
quitoes from  any  locality  would  carry  with  it  the  elimi- 
nation of  malarial  troubles  as  well.  It  may  be  inter- 
esting to  note  in  this  connection  that  the  species  of 
Anopheles  live  easily  in  settled  communities,  enter 
houses  freely  where  they  can  manage  it,  and  that  the 
female  passes  the  winter  in  the  adult  stage  in  cellars, 
coming  up  occasionally  into  well-warmed  rooms  and 
even  biting.  Normally,  they  do  not  become  active 
until  well  along  in  May  or  in  June,  when  eggs  are 
laid  by  the  female  which  has  been  fertilized  the 
previous  fall. 

All  stages  of  the  parasites  causing  the  various  forms 
of  malaria  have  been  followed  in  both  man  and  the 
mosquito,  and  no  part  of  the  history  above  given  is 
guess-work.  The  connection  between  the  Stegomyia 
mosquito  and  yellow-fever  is  equally  certain,  though  the 
specific  parasite  has  never  been  made  out  in  either  man 
or  insect.  Direct  experiment  has  furnished  convincing 
proof  of  the  connection,  and  the  treatment  of  yellow- 
fever  epidemics  has  entered  a  new  phase.  The  efficient 
work  done  in  the  Panama  Canal  Zone  has  demonstrated 
that  the  disease  is  quite  controllable  through  the  insect 
and,  incidentally,  collections  made  by  entomologists 
from  the  U.  S.  Department  of  Agriculture  at  Washing- 
ton, have  shown  that  this  Stegomyia  is  never  found 
away  from  human  settlements.  The  relation,  then,  is 
extremely  close  between  this  insect  and  man,  and  they 


THEIR  RELATION  TO  MAN  207 

are   both   needful   to   the   continued   existence   of    the 
disease. 

There  are  other  tropical  fevers  that  are  probably  as 
much  dependent  upon  other  mosquitoes,  but  we  know 
less  about  them.  We  do  know  that  several  forms  of 
bird  malaria,  due  to  species  of  Proteosoma,  are  also  de- 
pendent upon  mosquitoes  as  intermediate  hosts,  and 


FIG.  96. — The  Tsetse-fly,  Glossina  morsitans. 

how  many  diseases  of  other  animals  are  transmitted  by 
them  is  as  yet  matter  of  conjecture  only. 

A  species  of  Culex  very  closely  allied  to  our  common 
"house"  or  "  rain  -barrel "  pest  is  responsible  for  the 
transmission  of  that  tropical  disease  "filariasis"  which 
sometimes  causes  the  abnormal  enlargement  of  the 
lymphatics  and  thickening  of  the  skin,  known  as  "ele- 
phantiasis." Other  species  have  been  charged  with 
being  agents  in  the  transmission  of  leprosy,  but  this 
must  be  considered  "not  proven"  as  yet. 

In  all  these  cases,  the  mosquito  is  an  intermediate 
host:  not  a  mere  carrier,  but  a  fellow  sufferer  with 
man,  subject  to  another  form  of  the  same  disease, 


208 


INSECTS 


and  in  this  respect  there  is  a  fundamental  difference 
from  those  troubles  conveyed  by  house  flies,  which 
suffer  nothing,  and  are  purely  mechanical  transporters 
of  the  infection — albeit  peculiarly  well  adapted  for 
their  purpose. 

There  are  other  flies,  however,  that  seem  to  be  nearer 
the  mosquitoes  in  this  respect  and,  among  these,  are  the 
species  of  Glossina  or  "tsetse"  flies  of  South  Africa, 

which  are  known  to  pro- 
duce fatal  affections  in 
horses  and  have  been  re- 
cently charged  with  being 
agents  in  the  transmission 
of  the  "sleeping  sickness.  " 
All  mosquitoes  pass 
their  early  or  larval  stages 
in  water,  and  that  is  about 
the  only  feature  that  is 
common  to  all  of  them. 
They  differ  widely  in  the 
character  of  the  waters 
which  they  inhabit,  in  the 

FIG.  pT.-Larva^and^upa  of  the  house      period  of  development,  and 

in  the  number  of  broods. 

Some  pass  the  winter  in  the  egg  state,  some  as  larvae 
and  a  very  fair  proportion  as  adults.  All  the  species 
that  are  closely  associated  with  man  may  breed  in 
dirty  water,  and  some  in  such  as  is  absolutely  filthy. 
Culeoc  pipiens,  the  common  "house  mosquito," 
breeds  in  rain  barrels,  lot  puddles,  cess-pools,  gutters 
and  sewer  basins.  It  is  rarely  found  in  clean  water  and 
almost  never  in  streams  or  brooks.  The  eggs  are  laid 
in  a  mass  or  raft  on  the  surface  and  are  easily  seen  when 
their  character  has  once  been  recognized.  In  forty- 
eight  hours  the  larva  is  ready  to  hatch,  a  little  lid  drops 


THEIR  RELATION  TO  MAN  209 

from  that  surface  of  the  egg  that  rests  upon  the  water, 
and  the  minute  wriggler  slides  at  once  into  its  natural 
element.  This  "wriggler"  is  so  named  from  its  peculiar 
jerky  mode  of  progression.  It  has,  attached  to  its 
mouth,  a  pair  of  very  dense  brushes  of  fine  hair,  and 
these  brushes  are  kept  in  constant  motion,  combing 
from  the  water  and  into  the  mouth  the  minute  organisms 
upon  which  the  creature  subsists.  At  the  other  end  of 
the  body  is  a  cylindrical  tube  of  moderate  length,  at  the 
tip  of  which  are  the  spiracles  or  openings  to  the  breath- 
ing tubes,  by  means  of  which  air  is  secured  from  above 
the  surface  of  the  water;  for  the  larva  although  strictly 
aquatic  as  to  food  and  other  habits,  is  yet  dependent 
for  its  supply  of  oxygen  upon  the  outer  air,  and  must 
come  to  the  surface  at  short  intervals  to  breathe.  Indeed 
the  favorite  position  of  this  larva  is  to  hang  head  down 
in  the  water,  the  tip  of  the  tube  at  the  surface,  the 
mouth  brushes  hard  at  work  securing  food.  This  pecu- 
liarity of  the  insect  gives  us  a  certain  advantage  in  our 
efforts  to  control  their  increase,  for  a  film  of  oil  on  the 
surface  of  the  water  in  which  they  live  will  prove  rapidly 
fatal,  the  oil  entering  into  the  body  through  the  spiracle 
when  the  insect  attempts  to  get  air. 

In  from  five  to  seven  days  during  the  summer,  the 
larvae  are  full  grown  and  change  to  pupae  in  which  the 
outline  of  the  future  mosquito  can  be  made  out  hunched 
into  a  comma-shaped  mass.  This  pupa  also  gets  its  air 
supply  from  above  the  surface,  through  two  small, 
trumpet-shaped  tubes  on  the  thorax,  so  that  it  is  also 
fatally  affected  by  oil.  It  is  active  in  this  stage  when 
disturbed,  and  moves  about  rapidly  but  erratically,  by 
means  of  two  paddle-like  structures  at  the  end  of  the 
abdomen.  When  it  becomes  quiet  it  rises  automatically 
to  the  surface,  and  there  rests  until  ready  to  assume  the 
adult  stage,  which  is  in  from  one  to  three  days  in  summer. 
14 


210  INSECTS 

In  cool  or  cold  weather  all  the  stages  are  lengthened  and, 
whereas  eight  days  from  egg  to  adult  is  perhaps  a  normal 
period,  this  may  be  increased  to  two  or  even  three  weeks. 
The  adult  male  is  incapable  of  sucking  blood;  but  the 
female  is  ready  to  bite  twenty-four  hours  after  she  be- 
comes developed,  and  in  three  or  four  days  thereafter  is 
ready  to  lay  eggs.  The  life  period  of  the  male  is  always 
short,  since  his  only  function  is  to  fertilize  the  female. 
The  life  of  the  female  depends  upon  her  ability  to  find  a 
place  for  her  eggs.  When  she  has  placed  them  her  pur- 
pose in  life  is  filled  and  she  also  dies.  If  she  finds  no 
suitable  place  she  may  live  for  weeks  and  bite  several 
times.  Those  females  that  develop  late  in  fall  do  not 
feed  after  they  are  fertilized,  but  seek  some  convenient 
hiding  place  in  a  cellar,  barn  or  outbuilding  and  remain 
there  dormant  throughout  the  winter.  They  become 
active  again  in  May,  but  larvae  are  rarely  found  in  any 
number  until  well  along  in  June.  This  species  occurs 
throughout  North  America  and  a  close  ally  occurs  in  the 
old  world. 

The  yellow-fever  mosquito,  Stegomyia  calopus,  or 
fasciata  as  it  used  to  be  called,  is  a  smaller  species,  black 
in  color,  with  white  marking  on  the  body  and  legs.  It  is 
rather  a  pretty  creature,  an  inhabitant  of  the  more 
southern  states  and  of  the  tropical  and  subtropical 
regions  of  America  generally.  On  the  Atlantic  coast  it 
does  not  extend  normally  north  of  Virginia,  and  this 
marks  the  limit  to  which  yellow-fever  may  extend  under 
ordinary  conditions.  I  am  not  unmindful  of  the  fact 
that  yellow-fever  has  occurred  in  New  York  and  Phila- 
delphia; but  the  conditions  permitting  these  epidemics 
are  now  understood  and  cannot  be  again  reproduced. 

In  habit,  the  Stegomyia  is  not  unlike  C.  pipiens,  and 
like  it  breeds  in  all  sorts  of  dirty  water.  It  is  very  sensi- 
tive to  cold,  and  the  first  frost  puts  an  end  to  its  activi- 


THEIR  RELATION  TO  MAN 


211 


ties.  It  is  even  more  domestic  than  its  ally  and  seems 
to  be  confined  to  the  vicinity  of  human  settlements.  It 
is  as  susceptible  to  oil,  in  the  larval  stage,  as  any  other 
species  and  also  hibernates  as  an  adult.  The  eggs  are 
not  laid  in  rafts,  however,  but  are  placed  singly,  not 
even  necessarily  in  water,  and  may  remain  dry  for  a 
considerable  period  without  losing  vitality.  When  they 
do  become  water-covered  they  hatch,  and  the  life  period 
and  stages  are  similar  to  those  of  pipiens. 


FIG.  98. — The  yellow-fever  mosquito,  Stegomyia  calopus;  larva,  pupa,  adult. 

The  species  of  Anopheles  are  longer  and  more  slender 
than  the  Culex,  and  the  wings  are  usually  more  or  less 
mottled  or  "dappled."  The  adult  females  hibernate  in 
houses  when  they  can  get  in,  and  in  May  or  June  lay 
eggs  on  the  surface  of  water,  singly  or  in  little  groups, 
but  not  in  boats  or  rafts.  They  are  kept  afloat  by  a 
peculiar  lateral  supporting  structure  and  hatch  in  a  day 
or  two  after  they  are  laid.  The  resulting  larva  or  wriggler 
is  altogether  unlike  that  of  Culex  or  Stegomyia.  It  is 
flatter,  with  a  proportionately  smaller  head  and  a  much 
shorter  breathing  tube,  and  lies  flat  on  the  surface  of  the 
water.  It  has  similar  mouth  brushes  but  gets  its  food 


212  INSECTS 

from  organisms  that  float  on  the  surface  film.  Its  float- 
ing habit  enables  it  to  live  in  very  shallow  water,  and  in 
places  where  no  fish  except  the  smallest  top  minnows  can 
follow. 

For  breeding  places  the  species  of  Anopheles  select 
moderately  clean  water,  and  prefer  the  grassy  edges  of 
large  pools,  ponds  or  swamp  areas,  or  the  eddies  or  dead 
corners  of  sluggish  streams  or  ditches.  They  do  breed  in 
lot  pools,  however,  and  even  in  rain  barrels,  pails  or  tin 
pans.  Cess-pools,  sewage  water  or  dirty  gutters  are  not 
attractive  to  them. 

Despite  this  difference  in  habit  the  larvae  are  as  much 
susceptible  to  oils  as  are  those  of  Culeoo,  and  in  the  pupal 
stage  the  differences  are  much  less  pronounced.  While 
in  a  general  way,  the  species  of  Anopheles  are  referred 
to  as  malaria  carriers,  not  all  of  the*n  are  able  to  serve 
as  intermediate  hosts.  The  most  common  and  widely 
distributed  form  known  to  be  dangerous  is  A.  maculi- 
pennis,  which  has  two  fairly  well-marked  dusky  spots 
on  each  wing. 

None  of  the  domestic  or  house  mosquitoes  are  great 
travellers,  and  they  rarely  fly  for  any  considerable  dis- 
tance ;  but  there  are  species  breeding  in  the  salt  marshes 
along  our  coasts,  both  Pacific  and  Atlantic,  that  migrate 
long  distances  inland,  drifting  with  the  wind  twenty 
miles  or  more  in  a  single  night.  These  species  lay  their 
eggs  in  the  marsh  mud  and  winter  in  that  condition. 
The  larvae,  which  resemble  those  of  the  house  mosquito, 
develop  equally  well  in  salt  or  fresh  water,  and  mature 
in  about  ten  days  from  the  date' of  hatching.  In  the  egg 
stage  they  may  remain  dormant  for  months  and  perhaps 
for  years. 

There  are  many  other  kinds  of  mosquitoes  important 
as  nuisances,  but  not  a  menace  to  health,  whose  consider- 
ation here  would  carry  us  beyond  the  scope  of  this  essay. 


THEIR  RELATION  TO  MAN  213 

The  one  uniform  requirement  for  development — water  in 
which  they  may  breed — gives  us  the  clew  to  the  method 
of  control,  and  our  efforts  should  be  intelligently  directed 
to  eliminating  such  places  by  draining  or  filling  rather 
than  to  destroying  the  larvae  after  they  have  begun  to 
develop. 

Sometimes,  where  it  is  recognized  that  mosquitoes 
are  hibernating  in  numbers  in  a  house  or  cellar,  it  may 
become  desirable  to  attempt  their  destruction  during 
the  winter.  This  can  be  accomplished  by  fumigation 
with  either  stramonium  or  culicide.  Stramonium  is 
simply  the  powdered  leaves  of  "jimpson  weed,"  which 
grows  almost  everywhere  within  the  United  States,  and 
it  is  made  up  with  one-third  its  weight  of  saltpetre  to 
make  it  burn  better.  Eight  ounces  of  good  stramonium 
is  sufficient  for  1000  cubic  feet  of  space  and  the  fumes 
are  not  poisonous  to  man.  Culicide  is  a  combination  of 
equal  parts  by  weight  of  carbolic  acid  crystals  and  gum 
camphor.  Dissolve  the  carbolic  acid  crystals  over  a 
moderate  heat  and  pour  over  the  camphor  broken  into 
small  lumps;  the  acid  dissolves  the  camphor  and  the 
solution  is  permanent  when  kept  in  a  stoppered  jar.  It 
requires  three  ounces  of  this  culicide  for  every  1000 
cubic  feet  of  space  and  it  should  be  evaporated  in  a 
shallow  pan  over  an  alcohol  or  other  lamp.  This  will 
kill  flies  as  well  as  mosquitoes  and  is  not  dangerous  to 
human  life.  The  mixture  is  inflammable,  however,  and 
must  be  used  with  that  fact  in  mind. 

Whichever  of  these  materials  is  used,  the  room  to  be 
fumigated  must  be  made  as  nearly  air-tight  as  possible, 
and  must  be  kept  closed  at  least  an  hour  to  make  certain 
of  a  satisfactory  effect  on  the  insects. 

Fleas  are  specialized  flies,  adapted  for  a  particular 
mode  of  life,  and  their  habit  of  more  or  less  indis- 
criminate biting  has  laid  them  open  to  suspicion  in 


214 


INSECTS 


FIG.  99. — A  home-made  evaporating  outfit  for  "culicide,"  using  a  section  of 
stovepipe. 

various  directions.  Their  connection  with  the  spread  of 
the  "plague"  seems  to  be  demonstrated  and  that  disease 
is  now  fought  in  the  rats  from  which  the  fleas  transmit 
it  to  man. 


THEIR  RELATION  TO  MAN 


215 


Fleas  live  in  their  adult  stage  on  hairy,  warm- 
blooded animals,  feeding  on  their  blood,  and  their  trans- 
versely flattened  form  set  with  spines  all  directed  back- 
ward enables  them  to  move  about  freely  and  quickly. 
Their  eggs  are  dropped  in  the  dens  or  nests  of  their 
hosts,  and  the  larvae,  which  are  slender,  white  and 


FIG    100. — The  common  cat  and  dog  flea:   a,  the  egg;    b,  adult;   c,  pupa; 
d,  larva  coiled  in  silken  case;    e,  lar^a. 


worm-like,  live  on  the  dead  and  decaying  animal  and 
vegetable  matter  always  present  in  such  places.  In 
houses,  the  common  dog  and  cat  flea  is  able  to  develop 
its  larvae  in  the  material  accumulating  in  the  crevices 
between  floor  boards  and  similar  situations,  and  in  the 
adult  stage  almost  any  kind  of  flea  will  bite  any  warm- 
blooded animal  upon  which  it  may  happen  to  get,  even 
if  not  capable  of  maintaining  itself  there.  So  man, 
though  unfitted  because  of  his  hairless  skin  to  serve  as 


216  INSECTS 

a  host  for  fleas,  may  nevertheless  be  bitten  by  any  of 
those  infesting  any  of  the  animals  that  live  with  him 
or  in  his  dwelling  places. 

In  an  ordinarily  well-kept  house  flea  larvae  cannot 
develop;  but  occasionally,  when  such  a  house  has  been 
kept  shut  up  during  a  summer,  a  brood  of  larvae  may 
develop  and  become  annoying.  In  such  case  a  free  use 
of  gasoline  in  floor  cracks  and  similar  places  where  the 
flea  larvae  live  will  generally  give  relief. 

The  subject  as  presented  here  is  a  mere  outline  of 
what  is  known  and  believed;  there  are  other  insects 
that  undoubtedly  facilitate  the  spread  of  disease  in  man, 
directly  or  indirectly,  and  there  are  many  more  that  do 
this  for  other  vertebrate  animals.  Their  importance 
from  this  point  of  view  cannot  be  overestimated,  and  at 
the  same  time  it  is  eloquent  testimony  that  for  many 
ages  man  and  these  insects  must  have  dwelt  together,  to 
permit  so  close  a  union  as  identity  in  parasitic  affections 
argues. 


CHAPTER  X 

THEIR  RELATION  TO  THE  HOUSEHOLD 

SINCE  man  has  enjoyed  the  shelter  of  a  dwelling,  how- 
ever simple,  he  has  had  in  it  something  in  the  nature  of 
furniture  and  bedding,  and  he  has  usually  felt  the  need  of 
storing,  in  time  of  plenty,  supplies  that  might  be  drawn 
upon  in  seasons  of  want.  And  stored  products  of  all  kinds 
have  ever  been  attractive  to  those  insects  that  feed  upon 
dead  animal  or  vegetable  matter ;  not  necessarily  decay- 
ing or  decomposing  matter,  but  simply  that  which  is 
without  active  life  and  ready  to  return  to  its  original  con- 
stituents, whether  by  way  of  the  human  alimentary  canal 
or  in  any  other  manner.  Stored  seeds  are  not  dead  in  the 
strict  sense  of  that  term;  but  it  can  stand  here  for  that 
inactive  condition  of  vegetable  life  in  which  it  is  not  ca- 
pable by  any  process  of  growth  of  outrunning  or  opposing 
the  attacks  of  such  creatures  as  attempt  to  feed  upon  it. 

There  is  no  one  species  of  insect  that  is  confined  to 
human  habitations.  All  are  species  that  also  occur  under 
normal  outdoor  conditions,  and  that  could  continue  even 
though  every  trace  of  mankind  were  removed  from  the 
face  of  the  earth;  but  as  to  some  of  them  the  struggle 
would  then  be  very  seriously  intensified. 

We  might  arrange  the  species  that  associate  with 
man  so  closely,  in  the  order  of  the  manner  in  which 
they  affect  us,  and  that  would  be  the  better  method 
were  we  intent  only  on  a  treatise  dealing  with  house- 
hold pests;  but  I  have  preferred  to  follow  the  general 
scheme  of  dealing  with  the  orders  and  giving  those 
general  habits  that  have  induced  certain  of  their  mem- 
bers to  frequent  man's  neighborhood. 

217 


INSECTS 


I  begin  by  stepping  outside  the  insects  altogether 
and  dealing  with  the  common  house  "centipede"  or 
"thousand  legged  worm."  It  is  a  frail  yet  formidable 

looking  creature  with  a  large 
number  of  long  slender  legs, 
yellowish-gray  in  color  and 
mottled  with  blackish.  It  has 
a  pair  of  long,  many-jointed 
feelers  and  the  last  pair  of 
legs  are  unusually  extended 
so  that  they  give  a  weird  im- 
pression of  danger  that  makes 
most  people  hesitate  about  in- 
terfering, except  through  the 
agency  of  a  broom  or  similar 
weapon.  It  is  most  commonly 
seen  in  cellars  or  on  damp 
walls,  but  may  occur  almost 
anywhere  in  the  house,  and 
its  mission  is  quite  innocent; 
praiseworthy  in  fact,  for  it  is 
predatory  on  other  household 
insects,  feeding  on  roaches, 
bed-bugs,  moths  and  such  sim- 
ilar creatures  as  it  is  able  to 
get  hold  of.  The  specimens 
should  really  never  be  inter- 
fered with  at  all ;  but  few  per- 
sons like  their  looks  and  there 
is  neither  danger  nor  difficulty 
in  killing  them.  At  a  touch 

the  thing  collapses  into  a  struggling  mass  of  legs,  which 
continue  to  wiggle  for  some  little  time  after  they  are 
separated  from  the  body.  The  natural  habitat  of 
species  of  this  kind  is  under  the  bark  of  trees,  under  logs 


FIG.  10 1. — A  house  centipede,  Sou- 
tigera  forceps. 


RELATION  TO  THE  HOUSEHOLD 


219 


or  in  other  damp,  sheltered  situations.  There  is  a  small 
poison  gland  connected  with  the  mandibles  which,  howr- 
ever,  are  incapable  of  piercing  the  human  skin.  Nor  is 
the  poison  sufficient  in  quantity  and  character  to  cause 
any  appreciable  trouble,  even  if  by  any  combination  of 
circumstances  the  jaws  could  be  forced  into  the  flesh. 

Among  the  true  insects  the  lowest  or  most  primitive 
order,  the  Thysanura,  are  represented  in  houses  by 
several  species.  In  the  cellar 
of  the  farm-house  where  veg- 
etables and  other  provisions 
are  stored  in  quantity,  they 
occur  wherever  it  is  damp 
and  wherever  the  least  sus- 
picion of  decay  occurs.  There 
are  here  several  species  of 
bristle-tails  and  spring-tails; 
small  wingless  creatures, 
soft -bodied,  with  indefinite 
mouth  parts,  that  feed  only 
where  a  way  is  opened  to 
them  by  other  things;  but 
when  that  way  is  opened 

their  feeding  promotes  the  decay  that  first  gave  them 
entrance,  and  by  their  numbers  they  may  become 
troublesome.  Remembering  their  fondness  for  damp 
places  the  free  use  of  lime  and  thorough  ventilation 
will  serve  to  disperse  them.  Some  are  so  lowly  organ- 
ized that  the  tracheal  breathing  system  is  not  fully 
developed  and  oxygen  is  absorbed  through  the  damp 
skin.  To  such  creatures  dryness  is  fatal.  In  cities 
and  towns  few  of  these  insects  are  found,  and  prac- 
tically only  two  species  of  "bristle-tails,"  or  "fish- 
moths"  or  "silver-fish"  occur.  One  of  these  species 
is  quite  tough  in  texture,  somewhat  convex,  evenly 


FIG.    102. — A  spring-tail  or 
Podurid. 


220  INSECTS 

silvery,  and  found  only  in  cellars  or  damp  places; 
the  other  is  very  soft-bodied,  the  silver  mottled  with 
blackish  or  gray,  and  found  in  dry  warm  places  like 


FIG.  103. — The  silver- fish,  Lepisma  domestica 

kitchens,  bake-houses  and  pantries.  They  feed  on 
all  sorts  of  starchy  products  and  nibble  preferably  at 
bits  of  bread,  cake  and  the  like;  but  at  a  pinch  they 
gnaw  the  calendered  surface  of  paper  or  book  bindings, 
and  have  been  known  to  attack  the  glossy  surface  of  a 


RELATION  TO  THE  HOUSEHOLD          221 

shirt  front.  They  are  rarely  abundant  enough  to  be  a 
real  nuisance,  and  wherever  it  is  necessary  to  deal  with 
them  they  yield  readily  enough  to  pyrethrum  or  gaso- 
line whichever  may  be  indicated;  naphthaline  serves 
very  nicely  as  a  repellent  wherever  one  is  necessary. 
Ordinarily,  killing  the  specimens  as  they  come  under 
observation  answers  every  purpose. 

A  little  higher  in  the  scale  of  development  come  the 
"book  lice"  belonging  to  the  family  Psocidce,  allies  of 
and    somewhat   resembling   the 
biting   lice   that  have  been   al- 
ready dealt  with   in   their  rela- 
tions to  other  animals.    Indeed, 
as    a    rule    housekeepers    when 
they  notice  these  little   insects 
among  their  stores  of  linen  or 
in    dusty    corners    of    drawers, 
suspect    them    of    being    really 
parasites  or  true  lice.     But  all 
lice,   whether   of   the   biting   or 
sucking  variety,   are    awkward,        FIG.  104.— A  book  louse, 
slow-moving  creatures  on  a 

level  surface,  while  these  little  Psocids  are  active  and 
agile,  running  backward  or  forward  with  equal  readi- 
ness, and  so  spry  as  to  be  not  easily  captured.  When 
captured,  instead  of  being  tough  and  leathery  in  texture, 
requiring  an  effort  to  crush,  they  are  soft  and  go  to 
pieces  at  a  touch.  They  are  never  found  on  animals  of 
any  kind,  and  what  they  are  after  is  the  little  organic 
particles  that  they  get  from  any  sort  of  dry  animal  or 
vegetable  matter.  A  dead  fly  will  be  reduced  to  a  fine 
powder  by  them  in  a  few  days  when  they  are  abundant, 
and  in  collections  they  are  occasionally  something  of  a 
nuisance;  but  almost  any  pungent  odor  drives  them 
away,  and  besides  we  have  always  the  resource  of  not 


222  INSECTS 

leaving  anything  about  that  is  attractive  to  them. 
Camphor,  naphthaline,  oil  of  sassafras,  carbolic  acid, 
and  oil  of  peppermint  have  all  been  employed  with  good 
effect  and,  really,  almost  anything  answers.  Occasion- 
ally they  infest  an  old  straw  or  corn  husk  mattress  in 
great  numbers,  and  in  such  case  the  only  real  remedy  is 
the  fire.  Other  members  of  this  group  composing  the 
order  Corrodentia  or  "gnaw^ers,"  a  branch  of  the  great 
Neuropterous  series,  are  winged  and  live  outdoors,  as 
indeed  do  many  of  the  wingless  species;  but  always 
their  food  is  dried  animal  or  vegetable  matter,  so  that 
the  only  reason  why  any  species  occurs  in  our  houses  is 
that  the  materials  that  they  feed  upon  are  found  there. 
Scarcely  higher  in  development  so  far  as  structure 
is  concerned  are  the  Termites,  or  "white  ants;"  but 
though  low  in  physical  organization  they  are  most 
wonderfully  developed  en  the  social  side,  standing 
scarcely  inferior  to  the  true  ants.  Termites  are  not 
numerous  in  species  anywhere  in  temperate  or  frigid 
North  America,  and  throughout  most  of  our  country 
only  a  single  species  occurs  or  is  at  all  common — the 
Termes  ilavipes.  In  warmer  countries  and  in  the  trop- 
ics, the  number  of  species  is  much  greater,  while  in 
Africa  they  have  their  point  of  greatest  development. 
In  that  country  the  insects  themselves  are  house  build- 
ers, their  habitations  rising  in  many  cases  ten  feet  or 
more  above  the  surface  in  turret-like  form  and  clustered 
in  great  villages.  But  it  is  not  with  their  peculiar  or- 
ganization nor  interesting  social  life  that  we  have  to  do 
here;  but  with  their  habits  when  they  leave  their  own 
dwellings  and  invade  ours.  Yet  to  fully  understand  the 
creatures  and  how  they  come  to  be  with  us  at  all,  we 
must  know  a  little  of  their  history.  The  popular  term 
"white  ant"  is  derived  from  the  pale,  yellowish-white 
workers  of  the  common  species,  which  are  wingless, 


RELATION  TO  THE  HOUSEHOLD 


223 


about  one-fourth  of  an  inch  long,  flattened,  with  a  large 
head,  small  thorax  and  a  rather  large,  ovate,  bluntly 
terminated  abdomen  or  hind  body.  Outdoors  they  are 
usually  found  in  small  numbers  under  flat  stones  at  the 
edges  of  woods,  in  fallen  trees,  old  stumps  or  in  woody 
material  generally.  When  a  colony  is  disturbed  most  of 
them  will  dive  out  of  sight  into  galleries  underground 


FIG.  105. — Termes  flampes, — a,  larva;  b,  winged  male;  c,  worker;  d,  soldier; 
e,  female;  /,  pupa. 

and  seem  to  be  concerned  only  in  getting  away  as  fast 
as  possible.  They  are  very  soft,  helpless,  without  eyes, 
and  in  the  day-light  are  absolutely  defenseless.  A  few 
specimens  a  little  larger  in  size  will  appear  bolder  than 
the  rest,  not  quite  in  such  a  hurry  to  get  away,  and  when 
we  look  at  these  more  closely,  we  note  that  the  head  is 
larger  and  that  they  have  longer,  pointed  jaws  or  man- 
dibles. They  are  indeed  the  soldiers  of  the  colony,  and 
developed  for  its  defense;  but  very  helpless  soldiers  at 
that  when  uncovered,  because  like  the  workers  they  are 
wingless  and  blind.  Both  workers  and  soldiers  are 


224  INSECTS 

represented  in  both  sexes,  but  the  reproductive  organs 
are  undeveloped  and  neither  sex  is  capable  of  repro- 
ducing. If  we  get  at  the  home  of  a  large  colony  in  an 
old  tree,  in  late  fall  or  early  spring,  we  may  find  with 
these  white,  wingless  forms,  some  decidedly  larger, 
rusty  brownish  specimens,  which  have  well  developed 
long  wings  lying  flat  on  the  back  and  well  developed 
eyes.  These  are  the  males  and  females  which  during 
the  warm  days  of  spring  leave  the  parent  nest  in  a  body 
and  swarm.  They  are  sometimes  seen  emerging  from 
some  old  fence-post  or  house  timber  in  great  hordes 
and  for  a  short  time  fill  the  air.  Their  flight  is  very 
weak,  the  two  pairs  of  wings  being  unconnected  and 
very  similar  to  each  other,  and  when  they  have  mated 
they  disappear.  The  majority  of  all  these  specimens 
die  without  being  able  to  found  a  colony  and  the  method 
of  starting  varies  somewhat  with  the  species.  For  our 
present  purpose  it  will  be  sufficient  to  say  that  in  a 
developed  colony  there  is  one  queen  or  egg-laying 
female,  with  abdomen  so  distended  that  she  is  helpless, 
simply  oozing  eggs  which  are  taken  and  cared  for  by  the 
workers.  Or  there  may  be  several  "  complement al " 
females  which  have  never  left  the  nest  and  never  become 
fully  winged.  In  any  case  the  colony  consists  of  many 
thousands  of  individuals  and  from  the  centre,  where  the 
queen  resides,  galleries  extend  in  all  directions.  The 
food  is  usually  wood-fibre;  but  may  be  any  sort  of  dry 
vegetable  products  even  when  made  up  into  thread, 
paper  or  other  artificial  forms.  Because  they  are  blind 
the  workers  shun  the  light  and  always  work  in  burrows 
or  galleries,  first  eating  out  the  fibres  as  food  and  then 
using  the  excrement  to  form  cells  or  chambers  where  the 
raw  tissue  has  been  removed.  When  a  nest  of  Termites 
has  its  centre  near  a  wooden  dwelling,  the  galleries  may 
at  almost  any  time  reach  some  of  the  posts  or  supports: 


RELATION  TO  THE  HOUSEHOLD          225 

and  when  they  do,  the  insects  work  into  and  through 
the  wood  in  concealment,  until  suddenly  there  is  a 
collapse.  In  the  tropics  they  get  into  floor  boards  and 
the  furniture  resting  on  it,  always  mining  out  of  sight 
until  there  is  a  breakdown. 

Where  the  insects  are  plentiful  their  habits  are  well 
known  and  house  builders  use  all  sorts  of  precautions  to 
keep  them  out  and  never  leave  furniture  in  one  place 
very  long.  In  the  more  northern  countries  where  T. 
flavipes  only  occurs,  or  is  the  only  common  species, 
usually  fence-  or  stair-posts  only  or  the  timbers  of 
barns  and  other  out-buildings  are  attacked  and  then 
the  problem  is  getting  at  and  destroying  the  central 
nest,  which  is  usually  in  an  old  stump  or  log  not  far 
away-  Only  occasionally  do  they  get  into  the  beams  or 
timbers  of  dwellings  or  other  inhabited  buildings;  but 
when  they  do,  they  usually  work  until  the  timber  is 
ruined  before  their  presence  is  suspected.  In  such 
cases  there  is  nothing  to  do  but  remove  the  infested 
material  and  put  in  iron  or,  before  putting  in  another 
wooden  support,  treating  it  with  some  creosote  or  other 
poisonous  preparation  unless  the  central  nest  can  be 
found  and  destroyed.  They  have  been  known  to  get 
into  a  store-house  and  to  ruin  large  quantities  of  sup- 
plies before  their  presence  was  even  suspected,  and 
into  a  masonry  vault  containing  records,  leaving  the 
pile  of  books  and  records  fair  to  all  outward  seeming, 
but  a  mass  of  cells  and  excrement  behind  it. 

Yet  a  little  further  up  come  the  members  of  the 
order  Orthoptera,  including  some  of  its  most  unlovely 
fellows,  the  roaches;  but  also  a  few  that  have  appealed 
more  to  poets  and  dreamers  in  the  chimney  corner — 
the  crickets,  including  of  course  those  on  the  hearth. 
Crickets  are  generally  accidentals  and  their  presence  is 
usually  due  to  their  search  for  shelter.  They  are  suffi- 
15 


226  INSECTS 

ciently  catholic  in  their  tastes  to  exist  for  some  time  on 
such  scraps  as  they  can  find  indoors  and  so  the  cheerful 
chirp  is  not  infrequently  heard  in  some  country  locali- 
ties. But  there  are  other  species,  with  other  habits. 
In  sandy  districts  and  often  along  the  coast  where 
crickets  are  very  abundant  outdoors,  they  are  apt  to 
get  into  houses  in  their  general  wanderings  and  develop 
an  inordinate  fondness  for  woollen  goods,  especially  if 
they  are  at  all  damp.  It  has  been  my  fortune  to  accom- 
pany a  fisherman  on  an  early  spring  trip  to  the  club- 
house at  the  seashore,  after  it  had  been  closed  since  the 
preceding  fall,  and  I  watched  him  open  the  drawers  of  a 
bureau  containing  his  store  of  clothing,  and  then  I 
listened  to  his  expression  of  regard  for  the  crickets 
that  had  found  the  garments  so  toothsome;  and  I 
grinned  in  no  holy  joy,  for  that  same  fisherman  had 
always  regarded  insects  as  unworthy  of  consideration, 
and  knowledge  concerning  them  as  of  no  account  what- 
ever. And  lo,  now  he  was  forced  to  appeal  to  that 
knowledge  and  ask  advice!  It  was  all  very  easy  and 
meant  simply  have  everything  perfectly  dry  when  put 
away,  and  have  things  put  into  a  trunk  or  chest  rather 
than  a  drawer.  Where  crickets  do  get  annoying,  pieces 
of  soft  bread  dusted  with  Paris  green  or  white  arsenic 
will  soon  rid  the  house  of  them. 

As  for  roaches,  there  are  a  few  that  have  been  dis- 
tributed by  commerce  throughout  the  civilized  world 
and,  in  addition,  some  localities  have  species  of  their 
own  which,  while  living  chiefly  outdoors,  rather  com- 
monly get  indoors  as  well.  In  the  tropics  roaches  are 
most  numerous,  and  in  the  warmer  parts  of  our  own 
country  even  the  common  species  are  more  abundant 
and  troublesome  than  they  are  further  north. 

All  roaches  have  much  the  same  appearance  and 
general  habits.  They  are  flattened,  soft -bodied  with 


RELATION  TO  THE  HOUSEHOLD 


227 


long  spiny  legs,  long  slender  feelers,  and  the  head  bent 
down  so  that  the  mouth  comes  almost  between  the 
front  legs.  Some  are  winged  and  some  are  not;  but 
even  the  winged  species  do  not  as  a  rule  fly  readily  and 
some  never  at  all.  They  hide  in  crevices  during  the  day 
and  roam  abroad  at  night  seeking  what  they  may  de- 
vour, and  they  are  not  at  all  particular  what  it  is;  dry 
scraps  of  animal  matter,  moist  vegetable  matter — almost 
anything  indeed  that  can  be  eaten.  Moist  articles  are 


FIG.  106. — The  "Croton  bug,"  Ectobia  germanica:  a,  first;  b,  second;  c,  third; 
d,  fourth  stage;  e,  adult;  f,  female  with  egg  case;  g,  detached  egg-case;  h,  adult 
with  wings  spread. 


preferred  and  a  warm  wet  dishrag  which  was  not  washed 
after  using  has  almost  irresistible  attractions.  If  there 
was  only  one  roach  in  a  kitchen  and  I  wanted  that  roach 
I  would  place  just  such  a  rag  on  the  middle  of  the  floor 
soon  after  dark,  and  I.  would  expect  that  roach  there 
before  ten  o'clock.  This  applies  more  particularly  to  the 
large  oriental  roach  or  "black  beetle"  which  is  very 
heavy,  does  not  climb  much,  and  prefers  moist  places. 
The  "  croton  bug"  or  "German  roach"  is  a  much 
smaller  species,  climbs  readily,  and  favors  drier  places. 
It  is  much  bolder  than  the  oriental  species,  and  is  not 
infrequently  seen  during  the  day. 


228  INSECTS 

How  to  get  rid  of  roaches  is  a  question  frequently 
asked,  and  judging  by  the  number  of  infallible  roach 
powders  and  foods  on  the  market  is  one  frequently  and 
satisfactorily  answered.  Most  of  the  dry  powders 
depend  on  a  mixture  of  sugar  or  chocolate  with  borax, 
the  latter  being  the  killing  agent,  ihe  sugar  or  chocolate 
merely  to  attract.  Mix  equal  parts  of  sweet  chocolate 
and  borax  in  a  mortar,  so  as  to  mingle  thoroughly,  and 
spread  where  roaches  abound,  removing,  so  far  as 
possible,  all  other  food  particles. 

Roach  pastes  usually  contain  phosphorus  or  arsenic 
and  are  applied  on  pieces  of  soft  bread  which  is  a  favor- 
ite food.  An  ingenious  Australian  scheme  is  to  mix 
one  part  of  plaster-of-paris  with  three  or  four  parts  of 
flour  and  set  it  on  a  small  saucer  easily  accessible  to  the 
insects.  Feeding  on  this  makes  the  roaches  very  thirsty 
and  they  seek  water;  dishes  of  this  should  also  be 
placed  near  by  and  when  this  is  added  to  the  flour  and 
plaster,  the  latter  sets  and  clogs  the  intestines.  This  is 
a  very  simple,  safe  and  inexpensive  method,  and  once 
the  flour  and  plaster  are  set  out,  needs  only  attention 
to  keeping  up  the  supply  of  water.  In  any  case  when  a 
house  is  once  badly  infested  by  roaches  and  it  is  desired 
to  clean  them  out,  it  means  a  campaign.  No  one  appli- 
cation will  ever  be  successful,  but  persistence  will  be 
victorious  in  every  instance. 

There  are  many  interesting  peculiarities  about 
roaches,  but  none  greater  than  their  egg-laying  habits. 
The  entire  egg  supply  of  the  female  develops  simul- 
taneously in  a  sac  or  case  attached  at  the  end  of  the 
body,  technically  known  as  an  ootheca.  As  the  eggs 
develop  this  case  enlarges,  until  all  have  attained  full 
size  and  the  eggs  are  almost  ready  to  hatch.  Then  the 
female  drops  it  in  some  sheltered  corner,  the  seam  along 
one  side  splits,  and  all  the  young  roaches  come  out  at 


RELATION  TO  THE  HOUSEHOLD          229 

about  the  same  time.  As  a  matter  of  policy  it  is  always 
well  to  begin  a  roach  campaign  before  the  egg  cases 
have  been  fully  developed,  as  there  are  then  much 
fewer  specimens  to  be  dealt  with. 

The  Hemiptera  as  an  order  are  always  difficult  to 
place  in  a  linear  series  among  the  mandibulata,  but 
they  contain  one  species  that  must  be  referred  to  among 
the  forms  dwelling  with  man — the  "bed-bug,"  Cimex 
lectularius .  It  has  local  names  in  different  parts  of  the 


FIG.  107. — The  bed-bug  from  above  and  below  and  egg. 

country,  but  "bed-bugs"  are  always  recognized  even 
where  they  are  commonly  referred  to  as  "chinches." 
There  are  quite  a  number  of  the  Hemiptera  that  are  very 
much  flattened  and  fitted  to  live  in  narrow  crevices; 
but  none  more  than  this  bed-bug  which  occurs  now-a- 
days  only  in  connection  with  human  habitations.  An 
allied  species  lives  in  the  nests  of  swallows,  sometimes 
in  great  numbers,  but  does  not  infest  houses. 

The  pest  is  found  all  over  the  world  and  has  been 
recorded  ever  since  there  were  any  records;  so  there  is 
an  immense  fund  of  information  concerning  it — some 
true,  some  more  or  less  imaginary,  like  the  tales  of  the 


230  INSECTS 

ingenious  measures  adopted  to  reach  sleepers  in  beds 
which  had  been  isolated  so  that  they  nowhere  touched 
the  wall  and  had  the  posts  set  in  pans  of  water.  The 
bugs  are  normally  red  brown  in  color,  but  when  first 
hatched  or  when  compelled  to  go  without  food  for  a 
long  period,  they  are  almost  transparent  whitish. 
Just  how  long  they  can  go  without  food  seems  to  be 
not  definitely  determined,  but  it  is  certain  that  houses 
entirely  uninhabited  for  a  year  have  been  found  infested 
with  very  hungry  bugs  when  again  put  to  use.  The 
insects  moult  five  times  and  normally  feed  only  once 
between  moults,  a  period  of  five  or  six  days.  Nor, 
when  the  insects  have  fed,  do  they  always  or  even  usually 
stay  in  the  bed  occupied  by  the  victim.  On  the  con- 
trary, especially  where  there  is  a  metal  bed,  they  are 
very  apt  to  leave  it  and  seek  some  other  piece  of  furni- 
ture or  get  behind  base-boards,  picture  mouldings, 
trimmings  or  even  behind  the  backing  of  picture  frames. 
In  one  case  the  resort  for  a  considerable  colony  was 
found  in  the  large  old-fashioned  lock  on  the  room  door. 
In  the  large  wooden  bed  of  the  older  type  there  was 
usually  abundant  chance  to  hide  and  these  beds  were 
difficult  to  get  and  keep  clean,  especially  before  the  days 
of  gasoline.  In  such  cases  a  large  percentage  of  the 
bug  population  might  be  confined  to  the  bed;  but  the 
life  of  the  "chinch"  becomes  ever  more  difficult  under 
modern  conditions,  and  with  a  little  care,  practical 
exemption  is  securable  in  a  well-ordered  household. 
Their  occasional  introduction  is  almost  unavoidable 
where  public  conveyances  are  used.  I  have  seen  them 
in  railroad  cars,  trolleys,  boats,  omnibuses  and  carriages, 
and  have  noted  them  crawling  on  the  clothing  of  well- 
dressed  fellow  passengers  who  probably  did  not  bring 
them  in.  It  means,  therefore,  in  the  average  house- 
hold, a  more  or  less  continual  vigilance  on  the  part  of 


RELATION  TO  THE  HOUSEHOLD         231 

the  housekeeper,  and  one  of  the  first  and  most  charac- 
teristic signs  of  their  presence  is  the  round  black  spot 
produced  by  their  excrement  on  the  bed  linen  or  other 
places  where  they  have  rested.  Some  extremely  sen- 
sitive persons  recognize  their  presence  by  the  peculiar 
buggy  odor,  which  is  not  ordinarily  noticeable  until  the 
insects  are  handled.  Eggs  are  laid  in  the  crevices  in- 
habited by  the  adults,  in  small  batches,  and  oviposition 
extends  over  a  considerable  period.  They  are  whitish, 
oval,  reticulated,  and,  like  most  hemipterous  eggs,  of 
rather  large  size,  so  that  they  are  easily  seen  and  recog- 
nized. The  total  life  cycle,  from  egg  to  adult,  is  about 
forty-five  days,  and  the  insects  do  not  breed  during  the 
winter,  except  under  unusual  conditions. 

Given  an  ordinary  infestation  in  an  ordinary  bed- 
room, thorough  work  would  mean  taking  out  all  bedding 
and  taking  apart  and  examining  the  bed.  With  a  large 
bulb  pipette  force  gasoline  into  every  crevice  however 
small,  and  drench  the  binding  and  tuftings  of  the  mat- 
tress, wherever  there  is  a  folding  over  that  might  serve 
as  a  hiding  place.  Force  gasoline  through  the  pipette 
behind  and  under  the  base-boards,  under  the  picture 
moulding,  behind  all  the  trim  of  the  room,  and  into  all 
other  possible  hiding  places.  Treat  the  wash-stand, 
bureau  and  all  other  furniture  to  liberal  doses,  and 
carefully  examine  all  pictures  for  signs  of  either  eggs  or 
"spots."  If  necessary  remove  the  back  to  see  whether 
the  insects  have  made  their  way  under  it.  The  gaso- 
line will  kill  every  insect  it  touches;  but  not  the  eggs, 
so  that  a  second  treatment  must  be  made  to  reach  the 
insects  that  hatched  after  the  first.  It  will  require 
about  one  gallon  of  gasoline  for  a  bedroom  of  good 
size,  with  a  normal  amount  of  furniture,  and  the  ma- 
terial will  hurt  neither  fabrics  nor  paper.  Bad  infesta- 
tions in  hotels,  boarding-houses  or  tenements  are  best 


232  INSECTS 

reached  by  fumigation  with  hydrocyanic  acid  gas, 
which  will  be  described  later  on. 

In  the  southern  and  southwestern  states  there  is 
another,  much  larger  species  that  has  also  developed 
the  house  habit  and  is  known  as  the  "big  bed-bug,"  or 
the  "blood  sucking  cone-nose,"  Conorrhinus  sanguisu- 
'gis.  It  belongs  to  the  family  Reduviidce  or  "assassin 
bugs,"  all  of  which  are  predatory  in  habit,  and  its  bite 
is  a  serious  matter,  causing  much  swelling  and  often 
inflammatory  and  febrile  symptoms.  These  insects 
are  so  large  and  so  little  fitted  for  hiding  that  ordinary 
care  in  looking  after  beds  and  rooms  will  detect  them 
and  prevent  trouble. 

Among  the  Coleoptera  or  beetles  there  are  a  large 
number  that  live  with  us  and  cause  trouble.  All,  how- 
ever, are  species  quite  capable  of  taking  care  of  them- 
selves outdoors  and  come  to  us  only  because  we  have 
in  our  possession  or  in  the  building  some  of  the  products 
upon  which  they  normally  feed. 

A  good  illustration  is  found  in  the  species  belonging 
to  the  family  Dermestida,  nearly  all  of  which  are  feeders 
upon  dried  animal  products.  The  term  "dried  animal 
products"  is  a  broad  one  and  includes  little  scraps  of 
meat  left  on  an  old  bone,  a  bit  of  hide  remaining  where 
an  animal  has  decayed,  or  a  pile  of  hair  or  wool,  no 
matter  where  found.  A  dead  insect  found  in  the  field 
serves  as  a  nidus  in  which  an  egg  is  deposited,  and  if 
the  dead  insect  is  in  our  collections  that  is  not  a  matter 
of  concern  to  the  beetle,  provided  it  can  be  gotten  at. 
We  have,  therefore,  larder  beetles,  leather  beetles, 
museum  beetles,  carpet  beetles,  and  a  variety  of  others 
of  the  same  type,  all  seeking  in  our  dwellings  that  dried 
animal  food  which  they  require,  and  whose  presence  is 
indicated  to  them  by  the  discriminating  sense  of  smell 
with  which  they  are  fitted. 


RELATION  TO  THE  HOUSEHOLD 


All  the  members  of  this  family  are  dull  brown  or 
blackish,  clothed  with  gray,  white  or  colored  scales  ar- 
ranged in  more  or  less  distinctive  patterns.  They  are 
more  or  less  oval,  without  conspicuous  head,  and  with 
short  legs  and  feelers  that  can  be  retracted  and  folded 
close  to  the  body,  so  that  the  insect,  playing  'possum, 
looks  like  a  bit  of  dirt  or  other  fragment  among  the 
mass  in  which  it  lives.  The  larvae  or  grubs  that  do  the 
real  damage  are  .stumpy,  worm-like  creatures  set  with 
brown  hair,  often  with  a  longer 
brush  at  the  end  of  the  body, 
sometimes  with  a  series  of  tufts 
at  the  sides. 

The  carpet  beetles  are  best 
known  and  least  liked  of  all 
these  species,  and  in  the  adult 
stage  when  they  frequent  the 
flowers  in  our  gardens,  are 
rarely  recognized.  The  so- 
called  "buffalo-moth,"  in  the 
adult  stage,  is  really  very  pret-  FIG.  io8.—c.  the  larder  bee- 

.   ..       .,        «.  /•     1     MI-  tie;  a,  its  larva;  b,  larval  hair. 

ty,  with  its  lines  of  brilliant 
red  and  white  scales.  This  in- 
sect is  a  feeder  on  animal  hair,  and  that  accounts  for 
its  attacks  on  woollen  goods  and  feathers.  Its  close 
ally,  the  black  carpet  beetle,  has  similar  habits,  and 
both  sometimes  get  into  a  feather  pillow  and  create 
havoc.  Where  the  cover  to  the  pillow  is  of  the  right 
texture,  the  feather  fragments  are  occasionally  worked 
into  it  so  as  to  form  a  soft,  felt-like  covering,  that 
puzzles  the  enraged  housekeeper  when  she  discovers 
the  condition  of  her  feather  stuffing.  All  woollen  and 
feather  fabrics  are  attacked  and  fed  upon,  and  the 
best  way  to  prevent  trouble  is  to  keep  those  things 
not  in  actual  use  shut  up  until  midsummer.  After 


234 


INSECTS 


that  there  is  no  further  danger  from  these  species. 
Of  course  the  usual  repellents,  camphor,  naphthaline 
and  the  like  are  useful,  and  gasoline  is  an  excellent 
destructive  agent;  but  after  all,  care  and  protection  by 
tight  boxes  or  paper  bags  is  best.  When  carpets  on 
the  floor  are  attacked  and  it  is  not  convenient  to  take 
these  up,  a  liberal  use  of  gasoline  is  indicated,  until  no 
further  traces  of  the  insect  work  are  noted. 


FIG.  109. — d,  the  carpet  beetle;  a,  its  larva,  the  "buffalo  moth";  c,  pupa. 


Almost  every  museum  and  every  collector  of  speci- 
mens of  organic  natural  history  has  to  do  with  two  or 
three  species  that  attack  such  dry  products  by  prefer- 
ence, and  here  again  the  ordinary  repellents  are  brought 
into  use,  supplemented  by  a  free  use  of  bisulphide  of 
carbon,  ether  or  chloroform.  None  of  these  is  advisable 
in  ordinary  household  use  because  pf  either  expense  or 
danger,  so  there  is  no  necessity  for  going  into  details. 
The  larger  species  such  as  the  larder  beetles  are  usually 
controlled  by  screening  or  keeping  the  provisions  prop- 
erly covered.  The  leather  beetles  that  occur  more 
commonly  in  manufacturing  establishments  must  be 


RELATION  TO  THE  HOUSEHOLD 


235 


dealt  with  according  to  the  conditions  as  they  exist  in 
each  individual  case. 

Quite  a  different  series  of  species  attack  our  stored 
grains  and  other  vegetable  products.  The  largest  and 
most  conspicuous  of  these  are  the  meal  worms — long, 
yellowish,  slender  worm-like  grubs  with  a  brown  head 


CL 


FIG.  1 10. — a,  the  meal  worm;  b,  pupa;  c,  adult  beetle,  Tenebrio  molitor;  d,  its  egg; 

e,  antenna. 

and  anal  segment,  reaching  the  length  of  an  inch  or 
more.  These  live  in  meal  of  all  kinds  and  are  more 
common  in  the  barn  and  stable  than  in  the  house 
though  not  unknown  there  by  any  means.  The  parents 
are  oblong  flattened  black  beetles  nearly  three-quarters 
of  an  inch  in  length,  and  are  usually  found  in  the  same 
places  as  the  larvae.  Incidentally  these  meal  worms 
are  great  favorites  with  our  feathered  friends,  and  they 
are  raised  in  great  quantities  as  food  for  cage  birds  of 
various  descriptions. 


236 


INSECTS 


Allied  in  appearance  but  very  much  smaller,  come 
the  various  species  of  flour  and  grain  beetles;  the  larvae, 
very  slender  whitish  grubs,  not  much  over  an  eighth  of 
an  inch  in  length,  the  adults  equally  slender,  flattened 
brown  beetles,  less  than  that  length,  or  scarcely  attain- 
ing it.  They  accumulate  wherever  meal  or  grain  prod- 
ucts of  any  kind  are  kept  open  and  allowed  to  stand  for 
any  length  of  time.  In  pantries  or  closets  where  jars  or 


FIG.  in. — The  confused  flour  beetle,  Tribolium  confusum:  a,  adult;   b,  larva; 

c,  pupa. 

receptacles  are  never  entirely  cleaned  out  before  re- 
plenishing, they  find  their  best  opportunity  for  multi- 
plying, and  the  best  method  of  checking  them  lies,  in 
consequence,  in  cleaning  out  thoroughly  every  recep- 
tacle for  such  products  before  putting  in  a  new  supply. 
In  peas,  beans,  lentils  and  the  like,  "weevils"  often 
make  their  appearance,  and  that  is  manifested  when  in 
such  seeds  one  or  more  round  holes  about  one-sixteenth 
of  an  inch  in  diameter  may  be  noted.  Now  while,  ordi- 
narily, these  insects  breed  outdoors,  and  simply  pass  the 
winter  in  the  seeds  that  were  attacked  in  the  field;  yet 


RELATION  TO  THE  HOUSEHOLD 


237 


in  the  artificial  warmth  of  our  houses  the  beetles  emerge 
in  late  fall  or  during  the  winter,  and  lay  their  eggs  on 
the  dried  peas,  etc.,  so  that  what  may  be  a  pretty  fair 
lot  of  legumes  in  fall,  may  be  an  utterly  useless  lot  of 
vegetable  debris,  in  the  spring  following.  The  grubs 
in  this  case  are  chunky,  white  creatures,  curled  up 
inside  the  seeds,  and  the  beetles  are  small,  very  chunky 
gray  forms,  with  very  stout  hind  legs  and  the  hind  part 
of  the  abdomen  very  abruptly  terminated.  The  ordi- 


FIG.   112. — The  drug  beetle,  Sitodrepa  panicce:  a,  larva;  b,  pupa;  c,  d,  adult. 

nary  householder  sees  little  of  them  because,  as  a  rule, 
only  a  small  stock  of  such  products  for  almost  imme- 
diate use  is  at  hand;  but  to  the  farmer,  the  seedsman, 
the  grocer  or  other  dealer,  the  matter  is  sometimes 
serious.  Fortunately  we  can  reach  the  insects  even 
inside  the  seeds  by  the  fumes  of  bisulphide  of  carbon, 
in  a  manner  to  be  pointed  out  a  little  later. 

Then  come  those  species  that  get  into  more  solid 
vegetable  fibre,  like  roots,  stems  or  even  wood,  and 
many  of  these  belong  to  the  little  family  Ptinidcz  which 
contains  a  mixture  of  odd  and  bizarre  forms,  very 
different  and  yet  very  similar  in  general  character  and 


238  INSECTS 

habits.  The  drug  beetles,  Sitodrepa  panicea,  and  the 
cigarette  beetles,  Lasioderma  serricorne,  are  examples  of 
such  forms  and,  in  the  adult  stage,  are  little,  brown, 
more  or  less  cylindrical  species,  not  much  if  any  over 
one-tenth  of  an  inch  in  length.  The  eggs  are  laid  in  or 
on  almost  any  kind  of  wood  or  leaf  tissue,  and  the  larvae 
which  are  very  small,  curved,  white  grubs,  bore  into  this 
tissue  reducing  it  to  powder.  Cigarettes,  cigars  and 
plug  tobacco  are  often  attacked  and  little  round  holes 
through  the  surface  tell  the  tale  of  the  destroyer.  So 
the  roots  of  licorice  and  hellebore  are  equally  favorites, 
and  may  be  reduced  to  powder,  while  occasionally 
willow-  and  rattan- ware  is  seriously  injured. 

The  somewhat  larger  species  of  Hadrobregmus,  and 
the  species  of  Lyctus  or  powder  post  beetles  belonging 
to  the  same  family,  occur  in  the  woodwork  of  houses 
or  in  furniture,  and  may  create  serious  trouble.  They 
live  and  bore  in  the  seasoned  wood,  mining  it  in  every 
direction  and  in  time  reducing  it  to  a  mass  of  powder. 
Little  round  holes,  from  which  sometimes  little  masses 
of  sawdust  are  ejected,  declare  the  character  of  the 
insects  at  work  here,  and  for  them  there  is  no  one 
method  of  treatment.  Creosote,  gasoline,  tar,  paint 
and  similar  penetrating  or  covering  mixtures  are  ap- 
plied with  more  or  less  good  effect,  and  which  of  them 
is  to  be  used  depends  upon  the  especial  conditions  of 
the  attack. 

In  the  order  Lepidoptera,  the  "clothes  moths"  have 
become  adapted  to  a  life  in  our  dwellings  and  are  rarely 
found  elsewhere.  They  belong  to  the  great  group  of 
Tineid  moths  in  which  the  early  or  primitive  characters 
of  the  order  are  yet  well  marked,  and  as  a  relic  of  their 
ancestral  habits  they  retain  the  practice  of  making  cases 
or  shelters  in  the  larval  stage.  This  serves  as  a  protec- 
tion to  the  caterpillar  and  as  a  means  of  concealment; 


RELATION  TO  THE  HOUSEHOLD 


239 


for  being  made  of  the  material  among  which  the  insect 
feeds,  it  is  not  usually  conspicuous.  The  divergence 
from  the  usual  vegetable  feeding  habit  of  caterpillars 
is  a  specialization  that  is  quite  marked,  because  it  is 
not  only  a  feeding  upon  animal  tissue  but  upon  dried 
or  dead  animal  tissue.  In  Chapter  VII  it  was  pointed 
out  that  some  moths  lived  in  the  heavy  fur  of  certain 
animals  so  that  they  became  literally  moth-eaten  dur- 
ing their  lifetime,  and  this  habit  of  feeding  upon  such 


FIG.  113. — A  clothes  moth,  Tinea  pellionella,  with  its  caterpillar  in  and 
out  of  case. 


material  when  removed  from  the  animal  is  only  a  little 
further  specialization  in  the  same  direction.  It  fur- 
nishes, also,  an  explanation  of  why  woollens  and  ma- 
terials made  of  animal  hair  or  fibre,  in  whole  or  in  part, 
are  subject  to  moth  attacks,  while  linens  and  cottons 
are  practically  exempt. 

The  "moth"  itself,  or  " miller, "  is  a  small,  glisten- 
ing, light  yellow  creature,  with  very  slender,  long 
fringed  wings,  and  it  may  be  seen  fluttering  about  in 
the  dusk  of  early  evening  in  our  rooms  during  late 
spring  or  early  summer.  If  when  a  closet  door  is  opened 
at  this  period  a  number  of  these  moths  flutter  out, 


240  INSECTS 

there  is  a  probability  of  damage  already  caused,  and 
very  great  danger  of  more  damage  to  come.  Not  that 
this  moth  itself  has  done  or  is  capable  of  doing  any 
injury.  Its  mouth  parts  are  such  that  it  is  practically 
incapable  of  feeding  at  all,  and  altogether  incapable  of 
feeding  on  solid  tissue  of  any  kind.  But  it  lays  its  little 
whitish  eggs  in  the  woollen  or  similar  tissue  wherever  it 
finds  a  chance  to  do  so,  and  from  these  eggs  hatch  the 
little  caterpillars  whose  mouth  parts  are  formed  of 
sharp  jaws,  quite  fitted  for  cutting  the  animal  fibres 
among  which  they  live.  Almost  the  first  work  of  the 
caterpillar  after  hatching  from  the  egg  is  to  form  a 
little  case  from  the  tissue  among  which  it  finds  itself, 
held  together  with  silken  threads  of  its  own  produc- 
tion ;  and  this  case  is  enlarged  from  time  to  time  as  the 
insect  grows.  It  is  curious  how  these  individuals  differ 
in  habit.  Sometimes  the  cases  will  be  made  up  of  fibres 
of  all  colors,  indifferently  put  together  without  pattern 
or  system.  At  other  times,  and  that  is  rather  the  rule, 
the  color  first  selected  will  be  adhered  to,  so  that  in  a 
carpet  one  pattern  may  be  completely  eaten  out,  while 
others,  of  a  different  color,  will  be  untouched.  In  my 
own  experience  I  have  observed  a  very  decided  prefer- 
ence for  reds  where  such  were  obtainable,  and  in  rag 
and  brussels  carpets  I  have  seen  the  red  stripes  and 
flowers  eaten,  while  the  blue  stripes  and  green  leaves 
were  untouched. 

The  period  of  development  depends  on  the  tem- 
perature. In  the  more  northern  United  States  there  is 
only  a  single  brood;  in  the  middle  and  southern  states 
there  are  two  and  in  the  extreme  south  and  on  the 
Pacific  coast  there  may  be  more.  But  the  insect  is 
sensitive  to  cold  and  does  not  grow  or  develop  unless 
the  temperature  is  above  60°,  even  though  it  is  not 
killed  by  a  much  lower  degree.  Hence  has  come  the 


RELATION  TO  THE  HOUSEHOLD          241 

practice  of  placing  furs  and  other  valuable  articles  of 
apparel  or  drapery  in  cold  storage  where,  even  if  already 
infested,  no  development  can  take  place.  The  ento- 
mologists of  the  U.  S.  Department  of  Agriculture 
have  determined  that  a  temperature  of  40°  is  low 
enough  to  prevent  any  development,  and  my  own 
experience  in  the  household  is  that  until  a  daily  average 
of  60°  is  reached,  little  danger  is  to  be  apprehended; 
but  this,  of  course,  does  not  mean  that  in  closets  so 
placed  that  a  higher  average  temperature  is  main- 
tained, breeding  would  not  go  on  even  though  the 
outside  temperature  was  not  above  60°. 

To  prevent  infestation,  nothing  is  better  than  to 
brush  all  the  clothing  to  be  protected  and  then  pack  it 
into  tight  boxes.  They  need  not  be  heavy  nor  large 
boxes,  but  they  must  be  tight.  Pasteboard  boxes  will 
answer  every  purpose  if  the  covers  are  fastened  at  the 
point  of  junction  with  gummed  strips  and  such  boxes 
are  now  obtainable  of  almost  any  size,  for  garments  of 
all  kinds.  Heavy  paper  bags  answer  the  same  purpose, 
and  these  are  now  sold  for  that  purpose  in  the  larger 
cities.  They  can  be  easily  made  where  they  cannot  be 
bought.  Even  carefully  wrapping  in  newspaper,  using 
plenty  of  paper  and  covering  joints,  will  answer,  where 
the  garments  are  packed  away  in  trunks  or  moderately 
tight  drawers.  But  there  should  be  no  doubt  about  the 
freedom  of  the  garments  thus  put  away  from  "moths" 
or  their  eggs.  When  a  fabric  is  once  infested  and  the 
insects  cannot  be  reached  by  beating  or  brushing,  a 
drenching  with  gasoline  is  effective,  and  when  a  closet 
becomes  infested,  it  should  be  thoroughly  sprayed  with 
gasoline  so  that  every  crevice  is  reached  and  penetrated. 
Fumigation  with  sulphur  will  kill  them  if  properly  made, 
but  there  must  be  no  metal  and  no  fabrics  in  the  closet 
when  it  is  done.  Formaldehyde  vapor  is  ineffective. 
16 


242  INSECTS 

As  for  the  various  repellents  like  camphor,  naphthaline, 
tar,  etc.,  these  are  all  of  some  value  and  in  proportion 
to  the  tightness  of  the  drawer,  trunk  or  other  recep- 
tacle in  which  they  are  used;  but  none  are  implicitly 
to  be  relied  upon  if  the  fabric  is  already  infested,  or  if 
the  container  is  not  reasonably  tight.  Gasoline  will 
kill  every  caterpillar  that  it  touches  and  is  the  best 
material  to  use  where  rugs,  carpets,  hangings  or  drape- 
ries that  cannot  for  any  reason  be  removed  are  to  be 
dealt  with. 

We  have  further,  among  the  Lepidoptera,  and  in 
this  same  group  of  Tineids,  other  moths  and  their 
larvae  that  feed  on  our  stored  products,  but  hardly  in 
our  houses,  and  such  are  the  Indian  meal  moth,  Plodia 
inter  punctella,  the  Angoumois  grain  moth,  Gelechia 
cererella,  the  meal  snout  moth,  Pyralis  farinalis,  and  the 
like.  They  scarcely  come  under  this  head  for  detailed 
consideration;  but  should  be  mentioned  to  call  atten- 
tion to  the  fact  that  they  may  be  found  among  products 
often  stored  yet  hardly  to  be  considered  as  inhabi- 
tants of  the  household  itself. 

In  the  order  Hymenoptera  the  ants  are  not  infre- 
quent invaders  of  our  domestic  economy.  Sometimes 
they  come  in  merely  on  exploring  expeditions  from 
outside,  with  no  thought  of  remaining.  It  is  merely 
part  of  the  hunt  for  food,  and  if  something  is  found,  a 
squad  is  soon  at  hand  to  clean  it  out.  Among  such 
visitors  comes  the  large  black  carpenter  ant,  which 
nests  in  partly  decayed  logs,  branches  of  trees  and  the 
like,  and  forages  for  a  considerable  distance  round  about. 
A  house  near  a  large  nest  is  likely  to  be  so  frequently 
visited  as  to  make  them  a  nuisance,  and  to  abate  this 
the  colony  should  be  located  and  their  home  destroyed. 
This  general  recommendation  applies  to  any  species 
which  comes  in  as  a  visitor  in  this  same  way. 


RELATION  TO  THE  HOUSEHOLD          243 

Sometimes  ants  make  their  nests  just  outside  of  our 
houses,  on  the  lawns,  and  while  this  does  not  bring 
them  strictly  under  this  chapter  head,  we  may  digress 
for  a  moment  to  consider  them  as  a  nuisance.  With  a 
cane  or  other  stick  poke  a  few  holes  to  the  depth  of 
about  ten  inches  near  and  about  the  centre  of  the  nest, 
and  into  each  hole  pour  about  one  ounce  of  bisulphide 
of  carbon,  covering  the  hole  by  stepping  on  it.  The 
fumes  will  penetrate  throughout  the-  galleries  and  kill 
all  the  ants  and  their  Iarva3  that  are 
reached.  Usually  one  application  is 
enough;  if  by  any  chance  there  is 
renewed  activity  about  the  nest  a  few 
days  later,  repeat  the  application. 

Within  our  houses  three  or  four 
much  smaller  species  make  their 
homes,  and  establish  colonies.  There 
is  a  small  red  ant,  a  larger  black  ant, 
a  very  small  black  ant  and,  more 
occasionally,  a  very  small  red  ant. 
They  differ  materially  in  their  habits 
and  somewhat  in  their  life  cycle,  but  for  our  purpose 
are  enough  alike  to  be  considered  together.  Like  all 
ants  the  colonies  consist  of  a  queen,  a  large  number  of 
workers  and,  in  the  late  summer  and  early  spring,  also 
the  males  and  females  that  will  at  the  proper  time 
leave  the  nest  to  swarm.  Only  the  workers  are  seen  as 
a  rule,  and  these  swarm  over  everything  in  the  nature 
of  food,  and  cart  it  off  to  their  nests  which  are  situated 
behind  base -boards,  in  crevices  behind  the  plaster  or  in 
the  masonry ,  or  anywhere  in  the  shell  of  the  house  where 
they  can  establish  themselves.  Once  a  house  is  thor- 
oughly infested  the  task  of  getting  rid  of  them  becomes 
a  serious  one  and  can  be  accomplished  only  by  persistent 
work ;  but  it  can  be  accomplished.  In  the  first  place  lo- 


244  INSECTS 

cate  the  nests  if  possible  and  destroy  by  injecting  gaso- 
line or  bisulphide  of  carbon  with  a  syringe.  Both  of  these 
are  highly  inflammable  and  should  only  be  used  where 
there  is  no  fire  nor  open  artificial  light  of  any  kind. 
Many  colonies  may  be  reached  in  this  way  and  greatly 
weakened  or  destroyed.  Others  will  be  so  situated  that 
they  cannot  be  reached,  and  the  insects  will  simply  seek 
less  exposed  openings  into  the  rooms.  The  systematic 
campaign  then  consists  of  keeping  all  food  products  un- 
der cover  so  far  as  possible,  or  protected  by  belts  of  cre- 
osote or  oil  of  lemon,  which  the  insects  will  not  readily 
cross.  Set  out,  easily  accessible  in  their  ordinary  lines  of 
march,  all  the  raw  bones  with  small  particles  of  adher- 
ent meat  that  come  from  the  kitchen,  and  when  these 
become  covered  with  ants  throw  into  the  fire  and 
burn.  Or  with  a  knife  scrape  the  surface  of  a  piece  of 
meat  and  spread  the  scrapings  thinly  on  a  piece  of 
paper.  Burn  this  when  covered,  in  the  same  way, 
always  taking  care  to  let  none  escape.  Keep  this  up 
consistently  and  persistently,  and  no  matter  how 
numerous  the  ants  may  seem  to  be,  they  will  become 
so  greatly  reduced  in  numbers  that  the  nests  are  dis- 
organized for  lack  of  workers.  There  will  be  no  one  to 
feed  or  care  for  the  young  and  the  colonies  will  perish. 
Instead  of  the  meat  and  bone  method  the  sugar-sponge 
method  may  be  employed.  This  means  two  moderate 
sized  sponges,  saturated  with  sugar  water  and  pressed 
nearly  dry.  Place  one  near  the  run  until  the  ants 
swarm  in  all  its  cells;  then  remove  and  drop  into  boil- 
ing water,  substituting  the  second  sponge  in  its  place. 
The  boiling  kills  the  ants,  of  course,  and  the  sponge 
should  then  be  thoroughly  washed  to  get  rid  of  the 
dead  insects,  again  dipped  into  the  sugar  water  and 
prepared  to  replace  the  second  sponge  when  that  is 
ready  to  be  boiled.  It  is  sometimes  a  matter  of  weeks  and 


RELATION  TO  THE  HOUSEHOLD          245 

it  may  be  necessary  to  change  the  location  or  even  the 
character  of  the  traps  several  times;  but,  faithfully  car- 
ried out,  I  have  never  known  this  plan  to  fail,  and  I  have 
personally  employed  it  in  two  houses  occupied  by  me, 
when  the  insects  threatened  my  collection  and  ate  the 
fresh  specimens  on  the  setting  boards  when  not  protected 
by  carbolic  acid  belts.  This  plan  is  of  no  avail  against 
those  ants  that  come  in  merely  as  foragers  from  the  out- 
side, like  the  black  carpenter  ants  already  referred  to. 

Of  recent  years  a  species  of  ant  has  been  introduced 
into  one  of  the  southern  states  from  Argentina  that  is 
far  more  troublesome  than  any  of  our  American  species. 
It  bids  fair  to  spread  and  to  become  a  first  class  pest  so 
far  as  it  extends;  indeed  it  has  been  already  reported 
from  California  and  may  be  more  wide-spread  than  we 
now  believe.  It  is  known  as  Iridomyrmex  humilis,  and 
is  as  ready  to  establish  its  colonies  indoors  as  out. 
It  is  under  investigation  by  the  entomologists  in  that 
section  of  the  country  and  we  may  hope  that  before  it 
gets  much  further,  efficient  methods  for  its  control  will 
have  been  developed. 

In  the  order  Diptera  there  are  no  species  that  are  to 
be  considered  as  guests  except  the  common  house-fly, 
and  that  is  dealt  with  in  the  previous  chapter  in  its 
relation  as  a  carrier  of  disease.  So  the  flea,  which  gets 
into  houses  not  infrequently,  does  so  as  a  parasite  of 
the  dog  or  cat,  and  not  because  of  any  love  for  man 
himself.  Other  flies  there  are  in  the  house  not  infre- 
quently, but  in  most  cases  as  scavengers,  when  at- 
tracted by  decaying  or  fermenting  material,  hence  not 
strictly  to  be  dealt  with  here.  To  be  sure  we  have 
"skippers"  occasionally,  in  cheese,  especially  of  -the 
odorous  sorts,  and  sometimes  in  bacon  and  other  fat; 
but  they  come  very  decently  under  the  classification  of 
scavengers  and  need  not  be  further  considered  here. 


246  INSECTS 

And  now,  it  sometimes  happens  that  a  house  or  a 
room  long  neglected  gets  into  such  a  condition  as  to  be 
almost  uninhabitable  by  reason  of  insect  pests  of  all 
kinds — from  scavengers  to  parasites — and  the  question 
arises  whether  there  is  any  method  by  which  all  these 
things  can  be  reached  at  one  fell  swoop,  or  at  least  by 
two  swoops;  the  second  being  made  necessary  by  the 
fact  that  there  are  always  some  forms  in  the  egg  state 
and  not  to  be  reached  even  by  fumigation  with  hydro- 
cyanic acid  gas,  which  is  usually  recommended  under 
such  conditions. 

Hydrocyanic  gas  is  formed  by  the  action  of  dilute 
sulphuric  acid  upon  cyanide  of  potassium,  and  is  one  of 
the  most  penetrating  of  poisonous  vapors,  fatal  alike  to 
man  and  insects  and  even  to  plant  life  when  long  enough 
exposed  to  it ;  but  harmless  to  fabrics  and  not  injurious 
to  metals.  The  formula  for  each  100  cubic  feet  of  space 
to  be  treated,  is 

Cyanide  of  potassium,  98°  pure,  by  weight. .    i  ounce 

Sulphuric  acid,  sp.  gr.  1.83,  by  measure 2  ounces 

Water 4  ounces 

Break  the  cyanide  into  small  lumps  and  put  the 
necessary  amount  in  a  thin  paper  bag.  Put  the  water 
into  a  glazed  earthenware  vessel — a  wash  basin,  slop  jar 
or  other  bowl  will  answer — then  add  the  acid  slowly. 
The  water  will  heat  as  the  acid  is  added  and  will  fume 
or  bubble.  When  all  the  acid  is  added,  drop  in  the  bag 
containing  the  cyanide  and  get  out.  The  formation  of  the 
gas  will  be  retarded  for  a  few  moments  while  the  acid 
gets  through  the  paper  and  this  will  give  opportunity  to 
close  the  door  and  seal  it  as  tightly  as  possible.  The 
order  of  doing  this  is  important,  for  if  it  were  attempted 
to  pour  water  into  the  acid,  the  first  drops  would  cause 
a  boiling  so  violent  as  to  spatter  the  entire  volume  in 


RELATION  TO  THE  HOUSEHOLD         247 

every  direction.  It  is  also  well  to  have  the  vessel  large 
enough  to  hold  at  least  twice  the  amount  of  liquid 
required,  and  if  more  than  one  pound  of  cyanide  is 
necessary,  it  is  better  to  have  two  or  more  jars. 

Where  only  a  single  room  is  to  be  treated  make  it  as 
tight  as  possible  by  sealing  windows  and  other  exits, 
but  open  all  closets,  furniture  drawers  and  trunks  so  as 
to  give  free  entrance  to  the  gas.  When  the  exit  door  is 
closed,  place  a  damp  towel  or  other  cloth  at  the  bottom, 
plug  the  key-hole  with  cotton  and  leave  the  room 
tightly  closed  for  at  least  two  hours.  Then  open  a 
window  or  transom  from  the  outside  into  the  open  air 
or  into  a  well- ventilated  hall,  and  allow  the  gas  to 
escape  for  at  least  ten  minutes  before  entering  the 
room.  Open  all  windows  for  at  least  an  hour  before 
attempting  to  re-occupy  the  chamber. 

When  an  entire  house  is  to  be  treated,  first  of  all 
close  and  seal  all  windows  and  openings  to  the  outer 
air  as  tightly  as  possible,  except  those  through  which 
the  operators  expect  to  leave,  and  those  should ^be  on 
the  ground  floor.  Put  into  every  room  and  into  every 
hall  the  basins  or  jars  containing  the  necessary  amount 
of  water;  place  alongside  in  a  bottle  or  tumbler  the 
necessary  amount  of  acid  and  in  a  bag  the  cyanide. 
Begin  at  the  top  of  the  house,  because  the  gas  is  light 
and  rises;  first  pour  the  acid  into  all  the  jars,  then  add 
the  cyanide  and  repeat  on  the  floors  below  until  the 
entire  building  is  treated.  Two  men  can  work  better 
than  one  in  a  building  of  any  size,  and  in  such  cases  the 
number  of  fumigating  vessels  should  not  be  multiplied 
more  than  absolutely  necessary.  If  everything  has  been 
properly  prepared  it  is  a  matter  of  only  a  few  minutes 
to  start  fumigation  in  a  building  of  considerable  size, 
and  such  a  building  should  then  be  kept  tightly  closed 
for  twenty -four  hours  if  possible.  At  the  end  of  that 


248  INSECTS 

time  no  living  creature  not  in  the  egg  state  will  remain, 
and  the  house  can  be  opened  to  admit  fresh  air  and 
permit  the  escape  of  gas.  If  windows  can  be  opened 
from  the  outside  or  a  through  draft  can  be  obtained,  a 
few  minutes  will  answer,  and  if  a  scuttle  can  be  opened 
from  the  roof,  the  entire  house  will  be  safe  in  half  an 
hour  if  all  the  doors  in  the  halls  are  open. 

The  directions  for  use  here  are  much  more  formi- 
dable than  the  actual  work ;  but  the  danger  to  life  is  so 
great  if  proper  care  is  not  exercised,  that  undue  pre- 
cautions are  recommended  rather  than  general  direc- 
tions that  might  promote  carelessness. 


CHAPTER  XI 

THEIR  RELATION  TO  THE  FARMER  AND 
FRUIT-GROWER 

IT  was  emphasized  in  another  connection  that  insect 
species  that  are  naturally  abundant  are  so  because 
they  have  made  good  their  position  and  relative  num- 
ber as  against  all  their  checks,  and  so  long  as  natural 
conditions  prevail  they  will  maintain  that  abundance 
with  such  slight  seasonal  variations  as  may  be  caused 
by  temporary  favorable  or  unfavorable  conditions. 

When  civilized  man  enters  the  field,  serious  changes 
in  environment  are  produced  and  these  changes  are 
produced  faster  than  the  insect  and  other  life  can  adapt 
itself  to  them.  In  a  decade  a  wilderness  is  transformed 
to  a  farm  or  an  orchard,  and  the  balance  which  it  has 
required  centuries  to  establish  is  rudely  upset.  Those 
species  so  nicely  adjusted  to  their  surroundings  as  to 
barely  maintain  themselves  under  normal  conditions 
may  be  completely  crowded  out  by  the  destruction  of 
some  one  factor  that  permitted  survival,  and,  on  the 
other  hand,  conditions  may  be  changed  to  favor  such  a 
species,  so  as  to  permit  it  to  increase  out  of  all  propor- 
tion to  its  past  history. 

The  Colorado  or  zo-lined  potato  beetle,  universally 
known  as  the  "potato  bug,"  Doryphora  io-!meata,  was 
not  always  the  pest  that  it  is  at  present.  When  first 
discovered  in  the  foot-hills  of  the  Rocky  Mountains  it 
was  accounted  rather  a  rare  species,  that  barely  main- 
tained itself  on  the  scattered  indigenous  solanaceous 
plants.  But  when  civilization  brought  in  the  cultivated 
potato,  the  species  that  had  been  so  rare  that  it  had 

249 


250 


INSECTS 


practically  no  specific  natural  enemies,  found  condi- 
tions so  materially  changed  in  its  favor  that  it  increased 
by  leaps  and  bounds,  followed  the  trail  of  its  food  plants 
to  the  east,  and  in  a  few  years  over-ran  the  entire  area 
of  potato  cultivation. 

It  was  first  described  in  1824;   it  had  become  abun- 
dant enough  to  demand  the  attention  of  the  economic 


FIG.  115. — Colorado  potato  beetle:   a,  egg;   6,  larvae;   c,  pupa;   d,  adult  beetles. 

entomologist  in  1869,  when  Riley  wrote  concerning  it 
and  the  methods  to  be  adopted  for  its  control.  I  still 
remember  the  joy  that  possessed  me  when,  for  the  first 
time,  in  1874,  I  found  on  Long  Island  a  patch  of  pota- 
toes with  the  insects  present  in  all  stages.  They  had 
arrived  earlier,  but  I  had  not  been  fortunate  enough  to 
get  within  their  range  previously.  As  nature  works, 
all  this  is  so  very  recent  that  nothing  has  yet  developed 
in  the  way  of  an  effective  natural  check.  It  is  rarely, 
however,  that  an  insect  is  so  marvellously  favored  by 
the  changed  conditions  produced  by  man.  Usually  it 


RELATION  TO  THE  FARMER  251 

is  a  more  local  species  already  abundant  and  vigorous, 
that  derives  a  moderate  advantage  through  the  re- 
moval of  certain  of  its  natural  checks  and  the  greater 
facilities  for  getting  food. 

We  must  remember  that  an  injurious  insect,  as 
generally  understood,  is  not  necessarily  one  that  seriously 
injures  plants,  but  one  that  causes  notable  harm  to  any 
plant  or  part  of  a  plant  that  man  wants  for  his  own  use. 
The  farmer  looks  with  equanimity  upon  weedy  plants 
devoured  by  slugs  or  caterpillars,  but  raises  an  outcry 
when  his  cabbages  are  much  less  seriously  eaten.  Yet 
any  insect  feeding  on  a  cruciferous  weed  is  likely  at  any 
time  to  take  to  cabbage,  and  so  the  innoxious  species  of 
to-day  may  become  the  scourge  of  to-morrow. 

Among  the  factors  that  are  changed  by  the  farmer 
in  favor  of  the  insect,  none  is  of  greater  importance 
than  the  elimination  of  the  necessity  for  seeking  a  food 
supply.  In  nature,  plants  and  shrubs  of  one  kind  do  not 
often  grow  in  large  numbers  or  on  large  areas  crowded 
together  by  themselves.  Insects  are  therefore  com- 
pelled to  seek  their  food  and  the  difficulty  of  finding  it 
makes  a  very  important  check.  The  farmer  removes 
that  when  he  plants  orchards  and  fields  many  acres 
in  extent  and  puts  on  the  same  or  similar  crops  year 
after  year.  Clean  culture,  important  as  it  is  in  some 
directions,  destroys  the  shelter  of  ground  beetles,  of 
snakes,  toads,  lizards,  tortoises  and  similar  creatures 
that  feed  on  species  that  go  underground  to  pupate, 
like  the  plum  curculio,  or  hide  just  below  the  surface 
during  the  day,  like  the  cut- worms.  The  war  on  small 
rodents  is  especially  favorable  to  insects,  because  shrews 
and  mice  are  great  devourers  of  such  things.  Culti- 
vated areas  are  not  sought  by  birds  if  they  can  find 
other  quarters,  and  some  species  will  simply  not  go 
into  such  places  at  all,  even  if  they  are  never  disturbed. 


252  INSECTS 

Hiding  places  for  parasites  are  also  limited  and  that  is 
a  matter  of  great  moment,  for  some  species  seem  to  be 
dormant  or  in  hiding  for  very  long  periods.  Alto- 
gether, it  may  be  said  that  in  all  that  he  does  on  the 
farm  and  in  the  orchard,  the  farmer  and  fruit-grower 
favors  those  species  that  feed  upon  his  cultivated 
crops,  and  turns  the  natural  scale  against  their  enemies. 
That  he  does  not  suffer  more,  is  merely  an  indication 
that  these  bird  and  animal  friends  that  he  eliminates, 
and  even  the  predatory  beetles,  are  not  the  most  im- 
portant checks  of  the  injurious  forms. 

Another  way  in  which  man  interferes  with  the 
orderly  course  of  nature  is  in  the  introduction  of  plants 
from  other  countries,  well  adapted  to  live  in  the  new 
locality  but  unable  to  resist  the  insects  native  to  that 
place,  and  so  giving  them  an  undue  advantage.  But 
this  is  not  a  circumstance  to  the  mischief  done  when 
an  adaptable  insect  is  introduced  into  a  new  country 
where  it  is  unknown  to  the  parasites  and  predatory 
forms  native  to  that  country!  The  wine-growing  dis- 
tricts of  Europe  imported  from  America  some  of  our 
vigorous  American  stocks  and  with  them  the  Phylloxera 
as  well.  Now  the  Phylloxera  in  its  native  home  is  not  a 
serious  pest  and  there  was  no  reason  to  believe  that  it 
would  or  could  ever  become  such.  But  the  European 
vines  proved  absolutely  non-resistant  and  succumbed 
to  injuries  where  the  American  vines  would  have  shown 
no  sign.  The  attempt  to  control  this  insect  in  Europe 
has  cost  millions  of  dollars  and  it  is  still  an  annual 
charge  of  many  thousands  on  the  various  governments 
and  growers.  The  difference  between  the  American 
and  European  stocks  is  merely  a  matter  of  adaptation, 
our  native  varieties  having  become  used  to  the  insect 
when  present  in  normal  abundance.  There  is  no  specific 
native  enemy  to  the  Phylloxera  and  conditions  in  Euro- 


RELATION  TO  THE  FARMER 


253 


pean  countries  are  not  unduly  favorable  to  its  rapid 
multiplication.  Their  vines  are  simply  not  used  to  the 
attack  and  sink  under  it. 

So  on  the  other  hand,  we  have  a  long  list  of  insects 
in  North  America  introduced  from  foreign  lands.  The 
Hessian  fly,  the  cabbage  butterfly,  the  asparagus  beetles, 
the  elm-leaf  beetle,  the  cottony  cushion  scale,  the  black 
scale  and  the  San  Jose  scale,  are  only  a  few  of  the 
well-known  pests  that  have  been  with  us  for  some  time. 


FIG.  116. — Vedalia  cardinalis,  the  destroyer  of  the  cottony  cushion  scale: 
b,  larva;  c,  pupa;   d,  adult. 


Most  of  our  troublesome  forms  have  come  to  us  across 
the  Atlantic:  the  cottony  cushion,  black  and  San  Jose 
scales  came  to  us  across  the  Pacific.  The  former  never 
got  away  from  the  western  coast ;  the  latter  has  covered 
the  entire  country  and  has  become  the  most  generally 
troublesome  pest  of  the  horticultural  industry.  The 
cottony  cushion  scale  was  eliminated  by  a  brilliantly 
successful  experiment,  resulting  in  the  introduction  of 
the  specific  check  to  the  species  from  its  native  home. 
It  was  an  experiment  that  we  can  duplicate  at  any  time 
with  the  same  factors.  It  is  quite  a  different  matter  to 
import  parasites  and  predatory  forms  hap-hazard  to 


254  INSECTS 

control  or  affect  insects  with  which  the  imported  species 
is  not  familiar  in  its  native  home.  Here  we  are  not 
making  use  of  an  adaptation,  but  are  rather  attempting 
to  create  one.  Such  experiments  may  be  crowned  with 
success,  but  it  will  be  a  success  which  cannot  be  pre- 
dicted and  it  will  depend  on  factors  not  apprehended 
by  the  experimenter. 

While  we  have,  undoubtedly,  introduced  into  our 
country  numerous  first  class  pests — the  brown-tail  and 
gypsy  moths  among  the  latest — it  is  equally  true  that 
dozens  of  species  have  been  introduced  on  imported 
stock  or  in  other  ways,  that  have  never  secured  a  foot- 
hold; and  we  have  a  few  species  that  have  started  out 
as  if  to  sweep  all  things  before  them  and  have  gradually 
died  out  so  as  to  become  almost  extinct.  Two  such 
species  have  been  enemies  to  pear  trees — the  pear  midge 
and  the  sinuate  pear  borer;  the  latter  of  which  never 
got  much  beyond  New  Jersey,  after  destroying  nearly 
all  the  pear  trees  in  one  district.  One  species,  the 
"horn-fly,"  created  enormous  alarm  among  owners  of 
cattle  for  a  few  years,  swept  over  a  large  part  of  the 
United  States  and  Canada  in  less  than  a  dozen  years, 
and  is  now  so  rare  where  it  first  appeared  that  speci- 
mens are  at  a  premium  for  collectors.  In  none  of  these 
cases  are  specific  natural  enemies  to  be  credited  with 
the  disappearance  of  the  species.  Conditions  simply 
were  not  suitable  in  all  respects,  and  the  insects  failed 
to  adapt  themselves  with  sufficient  completeness  to 
survive  in  the  long  run. 

The  important  point  is  that  those  species  that  do 
survive  the  introduction  are  exceptional  in  vitality  and 
adaptability,  and  are  therefore  naturally  abundant  and 
able  to  maintain  a  lead  over  all  their  enemies.  If  the 
specific  parasite  or  other  check  of  such  a  form  does  not 
exist  in  the  new  country,  and  is  not  introduced  with  it, 


RELATION  TO  THE  FARMER 


25S 


a  destructive  increase  under  cultural  conditions  is  almost 
inevitable. 

Now  in  what  ways  do  insects  injure  the  crops 
and  cause  injury  to  the  agriculturist?  This  might 
be  answered  by  a  reference  to  Chapter  III,  but  it 
may  be  useful  to  take  up  some  features  more  in  detail, 
with  the  injury  rather  than  the  insects  as  the  prime 
objects  of  consideration. 

Plant  lice  do  their  mis- 
chief in  part  by  directly 
exhausting  the  plant  of 
sap,  partly  by  causing  dis- 
tortions of  growth,  and 
partly  by  preventing  the 
proper  maturing  of  the 
fruit,  be  it  on  shrub,  tree 
or  vine.  If  on  the  roots, 
the  plants  are  weakened 
or  often  killed  and  even 
trees  are  sometimes  seri- 
ously injured.  A  secondary 
cause  of  injury  is  due  to 

the  production  of  honey-dew  by  the  lice.  This  serves  as 
a  culture  medium  for  a  black  soot  fungus  which  often 
disfigures  tree  fruit  to  such  an  extent  as  to  make  it  un- 
salable. Some  of  the  scales  have  a  similar  habit  and  so 
do  some  Psyllids  and  Membracids.  The  enormous  re- 
productive powers  of  plant  lice  render  them  especially 
dangerous,  and  very  often  the  farmer  does  not  even 
see  the  nucleus  from  which  come  the  hordes  that  he 
finds  on  his  wheat,  his  cabbages  or  his  melons,  a  few 
days  later. 

During  a  spell  of  dry  weather  it  may  be  noticed 
that  the  oats  or  the  grass  is  showing  white  spots  or 
becoming  silver-tipped;  or  the  onions  begin  to  show 


FIG.   117. — Thrips,  with  antenna  and 
tarsus. 


256  INSECTS 

yellow  spots,  turning  white  later,  and  often  killing  the 
tops.  This  the  experienced  grower  will  recognize  as 
the  work  of  Thrips,  which  scrape  the  surface  so  as  to 
break  the  leaf-cells  and  exhaust  the  sap,  leaving  a  dead 
spot.  When  these  dead  spots  become  sufficiently 
numerous,  the  leaf  fails  to  fulfil  its  function  and  dies,  or 
is  only  a  burden  to  the  plant. 

Leaf-  and  tree-hoppers  do  similar  work  and  a  com- 
mon example  is  found  in  the  vineyard,  where  leaves 
often  turn  brown  in  summer  before  the  fruit  is  ripe, 
because  of  the  injuries  done  by  the  grape  leaf-hopper. 

Scales,  soft  .and  armored,  attack  trees  of  all  kinds, 
in  the  orchards,  in  the  forests  and  on  the  city  streets. 
Sometimes  they  are  so  small  and  inconspicuous  that  it 
requires  close  scrutiny  to  find  an  isolated  individual; 
sometimes  they  are  large  and  showy,  flaunting  their 
numbers  and  threats  as  far  as  the  tree  itself  is  clearly 
visible.  The  honey-dew  and  soot  fungus  produced  by 
the  soft  scales  have  been  already  referred  to.  Many  of 
the  armored  scales  produce  a  specific  effect  on  the  tree, 
besides  exhausting  its  juices.  In  some  cases  distinct 
pits  or  depressions  are  formed  on  the  surface  of  the  bark ; 
in  others  the  bast  is  discolored  and  poisoned  where  the 
puncture  is  made,  and  when  the  punctures  are  suffi- 
ciently numerous  the  bast  simply  fails  to  do  its  work. 
Peach  trees  infested  by  the  San  Jose  scale  sometimes 
reach  such  a  condition  in  fall  that,  after  growth  is 
completed,  the  bast  has  lost  all  vitality.  During  the 
winter  the  poison  does  its  work;  in  spring  the  tree 
starts  from  the  supply  stored  in  the  buds,  blossoms 
and  even  begins  to  leaf  out,  but  when  demand  is  then 
made  upon  the  roots  for  fresh  nourishment  the  bast 
fails  and  the  tree  dies. 

This  poisoning  effect  is  not  peculiar  to  scales,  but 
is  a  feature  in  many  other  of  the  Hemiptera.  Some  of 


RELATION  TO  THE  FARMER  257 

the  plant  bugs  of  the  Capsid  series  have  it  very  strongly 
developed  and  Coreids  like  the  common  squash  bugs 
are  well  known  for  the  poisonous  effects  of  their  punct- 
ures on  vines  and  other  plants. 

Some  plant  lice  form  galls,  sores  or  cankers  on 
branches,  trunk  or  even  the  roots,  like  the  woolly  louse 
of  the  apple;  and  some  of  these  canker  sores  offer 
excellent  points  of  entrance  for  germs  of  disease  and 
decay.  Indeed  it  has  been  charged  against  some  of  the 
species  that  certain  plant  diseases  are  either  carried  or 


FIG.  118. — Woolly  apple-louse  at  c,  showing  galls  made  on  roots  at  a, 
the  woolly  wingless  form  at  b. 


given  points  of  entrance  by  them.  The  root-feeding 
forms  are  particularly  dangerous,  because  until  the 
tree  or  other  plant  begins  to  show  bad  condition  there 
is  no  way  of  recognizing  their  presence. 

Not  all  the  injury  done  by  these  various  forms  of 
sucking  bugs  is  obvious,  and  so  used  does  the  farmer 
become  to  the  loss  that  very  often  he  does  not  appre- 
ciate it.  A  simple  experiment  made  by  one  of  our 
economic  entomologists  proved  that  leaf-hoppers  in 
grass  fields  in  his  state  were  so  numerous  that  they 
shortened  the  crop  one-half.  Demonstration  of  this 
was  made  by  dividing  a  meadow  into  two  equal  parts, 
pasturing  cattle  on  both,  but  collecting  the  leaf-hoppers 


2  S8  INSECTS 

by  means  of  hopper-dozers  on  one  part  only.  This  part 
supported  exactly  twice  the  number  of  cattle  during 
the  season  that  could  be  maintained  where  the  hoppers 
were  left  undisturbed. 

It  is  comparatively  easy  for  the  farmer  to  estimate 
his  loss  when  the  green-fly  drains  his  wheat  so  that 
instead  of  the  expected  twenty  bushels  he  harvests 
only  ten  or  none  at  all.  The  drain  upon  all  sorts  of 
crops  by  the  myriad  of  specimens  constantly  sucking 
plant  juices  and  reducing  the  yield  to  a  less  obvious 
extent,  is  rarely  capable  of  estimation,  but  varies  from 
ten  to  fifty  per  cent,  almost  every  year  on  most  of  our 
staple  crops.  This  sounds  like  an  exaggeration,  but 
every  person  who  has  ever  studied  the  problem  at  all 
carefully  will  agree  in  the  estimate,  I  think. 

And  then  come  the  host  of  species  that  feed  directly 
upon  leaf  tissue.  They  come  from  many  orders:  grass- 
hoppers, locusts,  crickets  and  their  allies  of  many 
kinds;  slugs  and  grubs  as  well  as  adult  beetles  in  great 
variety;  caterpillars  of  the  most  diverse  appearance 
but  always  great  devourers;  saw-fly  larvse  from  the 
Hymenoptera  and  a  few  maggots  from  the  Diptera  or 
fly  tribe.  Perhaps  no  kinds  of  insects  do  more  obvious 
injury  than  those  that  feed  openly  on  the  foliage  and 
yet  the  real  harm  that  they  cause  is  not  always  in 
proportion  to  their  feeding,  because  many  plants  and 
trees  will  support  the  destruction  of  a  great  percentage 
of  leafage  without  material  impairment  of  crops.  This 
does  not  apply  where  the  crop  consists  of  the  leaves 
themselves  as  in  cabbage,  spinach  and  other  vege- 
tables, all  of  which  have  their  own  particular  insect 
friends. 

Unfortunately  some  of  these  foliage  feeders  modify 
their  habits  somewhat,  on  occasion,  and  attack  more 
important  parts  of  the  plant,  e.g.,  when  the  rose-chafer 


RELATION  TO  THE  FARMER  259 

eats  by  preference  the  flowers  of  the  grape  and  thus  at 
once  destroys  the  crop  without  injuring  the  plant 
itself.  Some  cut- worms,  hiding  out  of  sight  during 
the  day,  cut  off  the  stalk  at  base  for  convenience  of 
feeding,  leaving  the  tops  on  the  surface  to  dry  and 
perish.  Or  they  climb  on  the  shrub  or  tree  and  eat 
out  the  buds  or  growing  tips,  destroying  the  crop  if 
not  the  plant. 

This  brings  up  the.  fact  that  in  his  method  of  culti- 
vation the  farmer  frequently  forces  upon  himself  an 
injury  which  the  insects  wrould  not  under  normal  con- 
ditions inflict.  If  a  field  be  left  fallow  or  in  grass  for  a 
year  or  two,  it  will  almost  inevitably  attract  the  night- 
flying  or  owlet  moths  of  the  family  Noctuida,  whose 
larvae,  the  cut-worms,  feed  normally  on  grasses  and  a 
great  variety  of  low  plants.  These  cut- worms,  or  many 
of  them,  winter  half  grown  in  sod  or  rubbish  on  the 
surface  of  the  ground,  coming  out  to  resume  their 
feeding  in  spring.  If  now,  in  early  spring,  the  farmer 
plows  this  infested  sod  and  plants  corn  or  potatoes, 
or  sets  out  cabbages,  tomatoes  or  sweet  potatoes,  he 
deprives  the  cut-worms  of  their  natural  food  and  prac- 
tically forces  them  to  take  what  he  has  set  in  its  place. 
Furthermore,  while  a  population  of  one  cut- worm  per 
square  foot  would  not  be  a  very  serious  infestation  in 
grass  land,  it  would  be  destructive  in  a  cornfield,  or  in 
a  cabbage  patch.  And  not  only  are  cut- worms  favored 
in  this  way:  there  are  weevils  known  as  bill-bugs, 
attacking  corn  planted  on  timothy  sod  or  following 
certain  other  grasses,  and  there  are  wire- worms  and 
white  grubs  that  attack  cultivated  crops  when  they  are 
put  in  after  grass  or  other  infested  plants.  Of  course 
this  means  bad  farm  practice  from  the  standpoint  of 
the  entomologist;  but  not  until  quite  recently  have  the 
farmers  been  willing  to  consider  any  modification 


26o  INSECTS 

merely  because  it  would  produce  conditions  less  favor- 
able to  insect  increase. 

Besides  those  species  devouring  foliage  above  ground, 
there  is  a  large  subterranean  population  of  wire- worms, 
white  grubs,  maggots,  slugs,  and  the  like  that  attacks 


FIG.  119. — A  bill-bug,  its  larva  and  work  in  root  of  Scirpus. 

the  roots  of  plants.  The  underground  work  of  plant 
lice  has  been  already  mentioned;  the  species  now 
referred  to  are  those  that  actually  devour  the  root 
tissue  or  dig  into  the  underground  stem  so  as  to  destroy 
or  weaken  the  overground  plant.  Cabbage,  onion, 
radish  and  other  root  maggots,  wire- worms,  grub- 
worms,  grape-root  worms,  root-borers — all  are  familiar 


RELATION  TO  THE  FARMER  261 

terms  to  the  farmer,  and  represent  sources  of  injury 
that  he  has  learned  to  dread. 

And  when  his  plants  have  developed  well,  his  fruits 
have  set  and  all  looks  fair  and  free  from  any  of  the 
pests  already  enumerated,  the  farmer  is  by  no  means 
certain  that  he  will  get  either  seed  or  fruit.  There  are 
numerous  midges  that  develop  in  the  ovaries  of  fruits 
and  flowers,  and  either  feed  directly  in  the  seed  or 
suck  its  juices  so  as  to  shrivel  it.  We  have  species  that 
attack  the  kernels  of  wheat,  rye,  oats,  sorghum  and 
other  grains;  others  that  get  into  the  ovaries  of  the 
clover  flower  and  destroy  the  seed — so  thoroughly, 
indeed,  that  in  some  localities,  while  it  is  easy  to  get 
good  crops  of  clover  hay,  it  is  impossible  to  get  any 
seed  at  all.  Midge  larvae,  indeed,  are  found  under  the 
most  divergent  conditions  and  their  injuries  are  by  no 
means  appreciated  as  yet  to  their  full  extent.  Not 
that  the  midges  are  alone  in  this  work,  for  among  the 
beetles  there  are  a  large  number  that  infest  special 
crops.  There  are,  for  instance,  the  BruMda,  contain- 
ing the  bean  and  pea  weevils  that  infest  seeds  of  all 
sorts  of  legumes,  from  the  pods  of  the  locust  tree  to 
those  of  the  lentil.  Sometimes  only  a  single  larva 
develops  in  a  seed  as  is  the  rule  in  peas,  or  there  may  be 
up  to  half  a  dozen  or  more  in  a  single  bean.  And  the 
worst  of  it  is  not  the  infestation  that  comes  in  the 
field  alone,  but  the  likelihood  that  without  great  care 
it  may  be  brought  and  continued  in  the  barn  or  store- 
house. Even  after  harvest  the  wheat  is  not  safe,  for 
if  it  be  left  in  shocks  in  the  field,  the  Angoumois  grain 
moth  is  apt  to  find  it  and  start  its  work  of  destruction. 

Further,  among  the  snout  beetles  we  have  species 
that  confine  their  attacks  to  the  buds  or  developing 
seed  capsules.  The  boll-weevil  of  the  cotton  is  perhaps 
the  most  conspicuous  example,  and  this  species  alone 


262  INSECTS 

has  demanded  the  expenditure  of  hundreds  of  thousands 
of  dollars  in  its  study  and  attempted  control,  and  has 
injured  the  value  of  the  crops  in  the  affected  states  by 
many  times  that  amount.  Less  conspicuous  but  equally 
destructive  on  a  smaller  area  is  the  strawberry  weevil, 
which  develops  in  the  bud,  preventing  the  formation 
of  fruit. 

This  habit  of  placing  the  eggs  in  a  protected  position 
or  with  reference  to  the  food  supply  of  the  larva  is 
quite  a  trick  among  the  snout  beetles,  and  some  of  their 
habits  are  very  interesting  as  well  as  economically 
important.  The  nut- weevils  have  the  snouts  very 
much  elongated  and  very  slender  so  that  they  are 
enabled  to  pierce  the  growing  burr  or  husk  and  place 
the  egg  in  the  developing  nut,  long  before  there  is  a 
shell  to  be  reckoned  with.  The  plum  curculio  cuts  a 
little  flap  from  the  surface  of  the  fruits  that  it  infests 
and  in  this  bit  of  loosened  tissue  lays  its  egg,  safe  from 
the  pressure  that  might  otherwise  be  exerted  upon  it 
by  the  growing  fruit.  And  so  it  is  with  other  of  the 
Rhynchophora  that  attack  our  fuits,  large  and  small. 

Even  tree  fruits  are  not  exempt  from  midge  attack, 
one  form  depositing  its  eggs  in  the  pear  bud  that  the 
young  larvae  may  be  in  position  to  get  down  into  the 
seed  capsule  while  yet  the  passage-way  into  the  ovary 
is  wide  open.  Other  flies  attack  growing  fruits  of  many 
descriptions  and  are  furnished  with  a  horny  ovipositor 
of  considerable  length  for  puncturing  the  skin.  Apple, 
orange,  olive  and  plum,  all  have  their  "fruit-flies"  that 
demand  toll  of  varying  importance. 

Among  the  Lepidoptera,  none  is  better  known  than 
the  codling  moth,  the  larva  of  which  feeds  in  apple, 
pear  and  quince.  Where  no  active  measures  are  taken 
for  its  control,  it  is  no  unusual  matter  to  find  from  90 
per  cent,  to  95  per  cent,  of  all  the  fruit  on  a  tree  wormy 


RELATION  TO  THE  FARMER 


263 


and  of  inferior  value.  This  species  seems  to  be  dis- 
tributed wherever  the  apple  is  grown.  Other  species 
attack  grapes  in  a  similar  manner  and  there  are  feeders 
among  the  smaller  caterpillars  in  or  on  almost  every 
fruit  that  grows.  Besides  feeding  on  or  in  the  fruits, 
many  of  them  are  also  miners  in  leaves  and  even  in 
twigs  and  branches.  There  is,  of  course,  a  great  deal  of 


FIG.   120. — Codling   moth   and  its  work:    a,  the  injury  done;    b,  place   where 
egg  was  laid;  c,  larva;    d,  pupa;    i,  cocoon;  /,  g,  adults. 


difference  between  the  amount  of  injury  caused  and 
usually  a  species  is  confined  to  either  one  kind  of  plant 
or  to  the  members  of  one  plant  family.  There  are  a 
few,  however,  that  are  obnoxious  to  a  variety  of  crops 
and  none  that  occurs  to  me  at  present  is  much  worse 
than  the  corn-worm,  boll-worm  or  tomato-worm,  as  it 
is  variously  named.  It  winters,  usually  in  the  pupal 
stage,  underground,  and  early  in  the  season  emerges  as  a 
yellowish,  inconspicuous  owlet  moth,  which  during  the 
month  of  May  in  the  middle  states  seeks  a  place  to  lay 


264 


INSECTS 


its  eggs.  At  this  time  the  most  attractive  things  seem 
to  be  the  early  peas,  and  very  soon  the  greenish  cater- 
pillars will  be  found  boring  into  the  forming  pods. 
As  the  young  corn  makes  its  appearance  this  becomes 
attractive  to  the  moths  of  the  second  brood,  and  the 
caterpillars,  now  usually  with  a  pale  reddish-gray  tinge, 


FIG.   121. — Heliothis  armiger:   a,  b,  eggs;    c,  larva,  ("corn- worm",  "boll- 
worm",  and  " tomato- worm  ");  d,  pupa  in  cell;  e,  f,  moths. 


appear  as  stalk-borers.  As  the  sweet  corn  advances  the 
caterpillars  find  the  forming  ears,  and  many  a  barren 
stalk  is  so  because  the  ear  has  been  eaten  even  before 
it  appeared  between  the  leaves.  About  this  time,  too, 
the  earliest  tomatoes  become  of  nice  size  and  offer 
another  outlet  for  the  caterpillars,  which  bore  into  the 
fruits  when  they  are  nearly  ready  to  color  and  take 
those  specimens  which  would  otherwise  have  sold  for 
fancy  prices.  In  the  southern  states  the  cotton  at  this 


RELATION  TO  THE  FARMER  265 

time  begins  to  offer  an  attraction  in  the  shape  of  form- 
ing buds,  and  a  little  later  the  "boll- worm"  makes  its 
appearance.  When  corn  is  plenty,  that  forms  an  at- 
traction superior  to  everything  else  and  then  come  the 
"corn- worms"  so  common  and  objectionable  in  the 
"roasting  ears."  Sometimes  there  is  only  one,  usually 
of  good  size;  sometimes  there  are  several,  usually 
smaller,  and  the  explanation  is  that  the  insects  are  very 
pugnacious  and  when  they  meet  they  fight.  When 
there  are  two  or  more  full  grown  larvae  in  one  ear,  it 
simply  means  that  they  have  never  chanced  to  meet. 
The  caterpillars  continue  in  the  corn  until  it  is  cut  and 
stacked,  and  some  may  yet  be  found  at  husking  time; 
but  from  the  time  the  kernels  begin  to  harden  they  go 
underground  as  they  mature  and  change  to  that  pupal 
stage  in  which  they  safely  pass  the  winter.  After  they 
once  get  started  in  spring  they  can  be  found  almost 
continuously  in  some  one  or  the  other  of  their  food 
plants. 

There  remains  yet  one  more  way  in  which  growing 
crops  are  attacked  and  that  is  by  borers,  and  these 
also  are  of  many  kinds  and  all  sizes.  The  stalk  of  wheat 
and  the  fruit  tree  fifty  years  old  are  equally  subject  to 
this  kind  of  injury,  and  larvae  of  Coleoptera,  Lepidopterat 
Hymenoptera  and  Diptera  all  contribute  to  the  mischief. 

Some  of  these  stem  feeders  really  do  not  deserve 
the  name  of  borers  at  all,  as  for  instance  the  larva  of  the 
Hessian  fly ,  which  attacks  wheat  stalks  at  the  base  and 
produces  a  gall  that  checks  growth,  or  the  joint- worm 
which  works  into  the  stem  at  a  joint;  but  for  conven- 
ience we  may  class  as  borers  all  forms  which  feed  out 
of  sight  in  stems,  twigs,  branches  or  trunks.  And  it  is 
astonishing  what  a  variety  of  borers  there  are  and  how 
generally  plants  are  infested.  Not  cultivated  plants 
only,  but  arrant  weeds  like  burdock,  thistle,  rag- weed 


266  INSECTS 

and  the  like.  We  find  among  Dipterous  larvae  maggots 
in  some  variety,  often  producing  swellings  or  galls  in 
herbaceous  stems,  besides  the  numerous  midge  larvae 
already  so  often  mentioned.  Hymenopterous  borers 
are  comparatively  few  in  number  and  chiefly  members 
of  the  saw-fly  or  horn-tail  divisions.  Some  of  these  are 
in  grasses  including  grains,  and  are  slender,  white, 
caterpillar-like  forms  which  often  hollow  out  the  entire 
length  of  a  stalk.  Pithy  stems  like  those  of  blackberry 
and  raspberry  are  favorites  with  this  kind  of  borers, 
not  many  of  which  belong  to  the  seriously  injurious 
class.  The  horn-tails  attack  woody  plants  more  gen- 
erally, but  are  also  comparatively  few  in  number,  both 
as  to  species  and  specimens. 

Lepidopterous  or  caterpillar  borers  we  have  in  great 
variety  and  in  all  kinds  of  plants  and  trees.  The  largest 
of  them  belong  to  the  Cossids  and  Hepialids,  the  giants 
among  the  so-called  Microlepidoptera.  Most  of  these 
are  confined  to  forest  trees,  and  it  is  notable  that  our 
only  really  troublesome  species  is  an  imported  one — 
the  wood-leopard  moth — that  attacks  shade  and  orchard 
trees.  In  this  connection  it  is  interesting  to  observe 
that  the  boring  habit  among  Lepidoptera  is  an  ancient 
one,  not  even  confined  to  terrestrial  vegetation,  and 
that  by  far  the  greatest  number  of  the  borers  of  the 
present  day  are  members  of  the  simpler  and  earlier 
types  of  Microlepidoptera. 

Wood-feeders  largely  we  find  in  the  Sesiid  clear- 
wing  moths,  among  which  are  some  of  our  most  trouble- 
some species,  e.g.,  the  peach  borer,  cherry  borer,  cur- 
rant borer,  blackberry  borer  and  the  like.  Some  live 
in  the  solid  wood  of  trunks  and  branches,  like  the  cherry 
borer  and  those  that  live  in  oak,  maple  and  other  trees: 
some  live  just  beneath  the  bark  and  make  chambers 
rather  than  galleries,  like  the  peach  borers:  others  are 


RELATION  TO  THE  FARMER  267 

in  roots  like  the  blackberry  crown  borer  and  the  grape 
root  borer;  while  yet  others  feed  in  the  centre  of  a 
stern,  like  the  currant  borer  or  lilac  borer.  Among  the 
Pyralid  moths  there  are  numerous  borers  in  herbaceous 
plants  and  among  the  Noctuid  or  owlet  moths  there  is 
quite  a  series  in  which  the  boring  habit  is  well  devel- 
oped; such  plants  as  potatoes,  tomatoes,  corn  and 
wheat  being  among  the  victims.  A  few  are  twig  borers 
on  trees,  like  those  working  in  the  terminal  shoots  of 
peach  and  plum. 

It  is  among  the  Coleoptera  or  beetles  that  boring 
habits  are  especially  well  developed.  There  is  almost 
no  sort  of  tree  or  plant  among  our  cultivated  species 
that  is  not  more  or  less  infested  by  coleopterous  borers 
of  some  kind,  and  in  a  very  general  way  that  same 
assertion  might  be  made  of  all  trees  and  plants.  So 
general  is  this  habit  that  except  in  the  predatory  and 
scavenger  forms,  there  is  scarcely  a  series  that  does  not 
have  some  sort  of  boring  species  included  in  one  or 
more  of  its  families.  The  Longicorns  and  Buprestids 
are  almost  all  borers  in  woody  tissue;  among  the 
Rhynchophora  or  snout  beetles  there  are  numerous 
borers  in  herbaceous  plants  and  a  goodly  representation 
that  works  in  woody  tissue.  Apple,  pear,  quince,  peach, 
plum,  nut  and  citrus  trees  are  all  more  or  less  subject 
to  attack,  and  grape,  blackberry  and  other  vine  and 
small  fruits  are  equally  apt  to  be  infested.  Potatoes 
have  weevil  borers  in  the  stem,  many  grasses  have 
similar  borers  in  the  roots,  and  even  cabbage  has  its 
leaves  and  stem  more  or  less  riddled.  Among  the 
tree  borers  there  are  two  rather  well-marked  types 
represented  by  the  round-headed  and  flat-headed  bor- 
ers. The  former  quite  usually  do  most  of  their  work 
in  solid  tissue,  the  latter  are  more  apt  to  make  channels 
in  the  bast  or  between  bark  and  sap-wood,  getting  into 


268  INSECTS 

the  solid  wood  only  to  pupate.  Some  of  the  round- 
headed  borers  have  similar  habits  but  on  the  whole 
they  are  more  diverse  in  their  methods  of  feeding  than 
the  flat-headed  borers.  With  both  we  have  species 
that  attack  only  dead  or  dying  tissue,  and  others  that 
will  feed  in  or  on  perfectly  healthy  trees.  Some  of  them 
must  have  matters  just  exactly  right,  like  the  twig- 
girdler  which  lays  an  egg  and  then  girdles  the  twig 
below  the  point  of  oviposition,  so  that  in  the  first  high 
wind  it  may  break  off  and  fall  to  the  ground.  Others 
like  the  oak-pruner  demand  living  wood  as  food  for 
the  larva,  but  a  dead  twig  for  pupation;  so  the  larva 
girdles  the  twig  from  the  inside,  leaving  only  a  thin 
shell,  makes  itself  comfortable  beyond  this  point,  and 
waits  the  time  when  it  is  blown  to  the  ground  to  com- 
plete its  transformations. 

Another  important  series  contains  the  bark  beetles 
which,  while  they  do  not  so  much  affect  the  horticul- 
turist, do  most  seriously  affect  the  forester  and  the 
lumberman.  It  would  hardly  pay  to  go  at  much 
greater  length  into  the  different  kinds  of  borers,  be- 
cause the  fact  of  general  infestation  has  been  suffi- 
ciently brought  out. 

We  see  from  this  brief  review  that  from  the  time  the 
plants  first  show  above  ground  until  the  harvest  is  in, 
they  are  subject  to  the  attacks  of  sucking  and  chewing 
insects  in  all  their  parts,  and  that  neither  root,  stem, 
leaf,  fruit  nor  seed  is  free  from  liability  to  infestation 
and  injury.  Some  of  this  liability  is  increased  by  inju- 
dicious farm  practice,  some  of  it  is  the  consequence  of 
past  carelessness,  and  a  portion  is  due  to  the  inevitable 
change  in  the  balance  of  nature  caused  by  culture  and 
by  planting  large  areas  in  one  sort  of  vegetation. 

It  follows  that  the  agriculturist  and  horticulturist 
is  always  at  war  with  insects,  either  actively  or  pas- 


RELATION  TO  THE  FARMER  269 

sively,  and  he  always  suffers  some  injury,  large  or 
small  in  proportion  to  the  activity  of  his  campaign 
against  them.  What  is  not  always  realized  by  the 
passive  resistant  is  that  what  he  loses  is  all  profit. 
It  costs  about  so  much  to  prepare,  plant  and  harvest 
an  acre  of  corn,  wheat,  potatoes,  cabbage  or  other 
crop,  and  if  the  insects  eat  10  per  cent,  of  what  would 
have  been  produced  had  they  been  destroyed,  that  10 
per  cent,  is  directly  out  of  the  farmer's  pocket.  And 
if  in  two  orchards  of  the  same  variety,  producing  exactly 
the  same  number  of  barrels  of  apples,  those  from  the 
one  are  clean  as  the  result  of  an  active  campaign  and 
the  latter  gnarled  and  wormy  from  curculio  and  codling 
moth,  the  difference  in  price  between  the  fancy  fruit 
selling  at  the  top  of  the  market,  and  the  other  fit  only 
for  the  cider  mill,  is  the  measure  of  loss,  since  the  cost  of 
handling  and  growing  is  practically  identical. 

It  has  been  attempted  again  and  again  to  calculate 
and  estimate  the  annual  loss  of  agricultural  products 
due  to  insect  ravages  in  the  United  States  and  Canada, 
and  no  one  has  fixed  it  in  figures  of  less  than  hundreds 
of  millions.  As  a  matter  of  fact,  the  money  loss  is 
difficult  of  estimation,  because  any  material  addition  to 
the  amount  of  a  crop  might  have  a  decided  influence 
on  its  price.  It  is  not  uncommon,  for  instance,  for  a 
farmer  to  make  more  money  on  a  short  crop  than  out 
of  an  excessive  one,  and  this  factor  has  been- previously 
noted  by  Dr.  L.  O.  Howard,  in  his  discussion  of  the 
same  subject.  A  better  basis,  perhaps,  is  the  percent- 
age of  crop  destroyed,  and  that  has  been  estimated  at 
anywhere  from  10  per  cent,  to  25  per  cent,  of  the  total. 
The  careful  student  will  be  inclined  to  consider  the  10 
per  cent,  estimate  too  low;  it  is  doubtful  whether,  in 
actual  lessening  of  crop,  it  will  reach  the  25  per  cent, 
mark;  but  if  we  take  into  consideration  the  lessened 


2  7o  INSECTS 

value  of  much  of  the  crop  actually  harvested  and 
marketed,  I  believe  that  20  per  cent,  depreciation  in 
value  of  farm  products  is  not  too  high  an  estimate  of 
the  losses  annually  caused  by  insects  in  the  United 
States  and  Canada.  As  the  value  of  such  products 
was  estimated  in  the  Report  of  the  U.  S.  Department  of 
Agriculture  for  1907  at  $7,412,000,000,  the  estimated 
loss,  due  to  insect  ravages  in  the  United  States  alone 
should  be  put  at  $1,500,000,000  at  least. 


CHAPTER  XII 

THE  WAR  ON  INSECTS 

HAVING  detailed  the  character  of  the  injury  done 
by  insects  and  given  some  idea  of  its  extent,  the  question 
arises;  what  can  we  do  to  prevent  such  loss,  and  what 
has  been  done  in  this  direction?  There  is  yet,  in  the 
older  settled  portions  of  our  country  a  rather  widely 
distributed  feeling  that  as  insects  exist  and  feed  on 
plants,  they  were  created  for  that  purpose  and  that  it 
is  meddling  with  a  divine  institution  to  attempt  their 
destruction  or  limit  the  amount  of  injury  done.  It  is 
the  same  sort  of  spirit  that  protests  that  "it  can't  be 
done"  whenever  any  attempt  is  made  to  better  sani- 
tary conditions,  to  control  the  spread  of  disease  or  to 
limit  the  agencies  that  make  for  the  spread  of  infection. 
Supplemented  by  the  equally  wide-spread  conviction 
that  any  grown  man  that  engaged  in  so  trifling  an 
occupation  as  the  collection  and  study  of  insects  must 
of  necessity  be  deficient  in  intellect  or  of  unsound 
mind,  this  condition  was  responsible  for  retarding  the 
development  of  economic  entomology  to  the  middle  of 
the  last  century,  and  even  then  it  developed  slowly 
and  failed  of  general  appreciation. 

With  the  establishment  of  agricultural  experiment 
stations  under  the  Hatch  Act  of  1887  conditions  began 
to  change.  Entomologists  were  appointed  in  several  of 
them;  their  work  began  to  make  itself  felt,  its  im- 
portance began  to  be  appreciated,  arid  now  there  is 
scarcely  a  state  or  territory  in  which  there  is  not  at 
least  one  working  economic  entomologist.  In  1889  an 
Association  of  Economic  Entomologists  was  formed 

271 


272  INSECTS 

with  about  a  dozen  members.  In  1907  there  were 
enrolled  among  the  active  and  associated  members, 
most  of  them  in  official  positions,  no  less  than  211 
names;  and  that  does  not  include  all  of  them.  Of 
foreign  associates  interested  in  the  same  line  of  work 
there  are  forty-five,  and  that  includes  most  of  those  in 
official  positions.  In  1888  there  were  less  than  half  a 
dozen  makers  of  pumps  or  machinery  suitable  for 
insecticide  work,  while  nozzles  were  difficult  to  obtain 
and  poor.  At  present  there  are  numerous  makers  of 
machinery  and  each  of  them  presents  a  long  line  of 
pumps,  nozzles  and  fittings  for  applying  insecticides 
and  fungicides.  On  the  Pacific  Coast  the  problems 
were  somewhat  different  from  those  of  the  Atlantic 
Coast  and  the  line  of  development  in  the  production  of 
insecticides  and  spraying  machinery  w^as  also  different. 
Fumigation  with  hydrocyanic  acid  gas,  the  lime  and 
sulphur  and  resin-washes  are  Pacific  Coast  contribu- 
tions; the  development  of  the  arsenical  sprays  and  the 
mineral  oil  preparations  are  to  be  credited  to  the  Atlan- 
tic Coast,  or  at  least  to  the  territory  east  of  the  Rocky 
Mountains,  for  much  of  the  pioneer  work  with  insecti- 
cides was  done  in  Illinois  and  Missouri,  by  Walsh 
and  Riley. 

In  1889,  every  ounce  of  kerosene  emulsion  was 
home-made,  and  Paris  green,  London  purple,  helle- 
bore, tobacco  and  pyre  thrum  were  practically  the  only 
insecticides  on  the  market.  There  was  whale  oil  soap 
also,  but  expensive  and  an  unknown  quantity  as  to 
its  ingredients.  Now  there  are  a  large  number  of 
manufacturers  throughout  the  country,  producing  com- 
mercially -every  preparation  that  has  proved  useful  in 
the  hands  of  experimenters,  and  chemists  everywhere 
are  seeking  to  improve  and  cheapen  the  known  combi- 
nations or  to  devise  new  and  more  effective  ones.  Mis- 


THE  WAR  ON  INSECTS  273 

cible  oils  and  lime  and  sulphur  combinations  are  made 
and  shipped  in  car-load  lots,  while  arsenate  of  lead, 
absolutely  unknown  as  an  insecticide  in  1888,  is  sold  in 
ton  lots  to  individual  purchasers. 

This  development  in  the  face  of  at  least  passive 
opposition  could  not  have  taken  place  in  so  short  a 
time  as  twenty  years  had  it  not  been  promptly  dem- 
onstrated that  the  fight  was  a  paying  one.  And  when 
the  reader  who  remembers  the  fruit  markets  of  that 
earlier  period,  compares  them  with  the  magnificent 
productions  in  our  markets  at  present,  he  will  realize 
the  advance  that  has  been  made.  Farming  and  fruit 
growing  has  been  developed  as  a  science,  along  scien- 
tific lines.  The  soil  is  a  chemical  laboratory,  with 
elements  ready  to  be  combined  into  organic  compounds 
under  proper  conditions.  The  plants  produced  in  this 
soil  and  from  these  elements  serve  naturally  as  food 
for  man  and  other  animals,  including  insects.  Man 
wishes  to  get  it  all  for  his  own  use  and,  of  course, 
therefore  desires  to  eliminate  the  insects  as  partners. 
Can  he  do  it,  and  if  so,  how? 

To  the  first  part  of  the  question  we  answer  yes,  to  a 
very  great  extent;  to  the  second  there  is  a  less  definite 
answer  since  every  group  of  species  must  be  dealt  with 
according  to  its  kind  and  no  one  application  will  serve 
for  all  kinds  of  species.  Often,  indeed,  where  insecti- 
cides cannot  be  used  at  all,  we  can  circumvent  by  plant- 
ing at  proper  times,  rotating  crops  so  as  to  prevent 
undue  increase,  and  by  harvesting  so  as  to  destroy  the 
insects  before  they  mature.  In  the  garden  and  in  the 
greenhouse  where  conditions  are  more  under  our 
control,  injury  from  insects  can  be  reduced  to  a  mini- 
mum, and  the  records  from  our  orchards  show  that 
wormy  fruits  are  not  necessary  features  in  a  crop. 

We  have  learned  that  as  against  practically  all 
18 


274  INSECTS 

insects  that  chew  their  food  and  feed  openly  upon 
plant  tissues,  arsenical  preparations  may  be  used  with 
good  effect.  Up  to  within  a  few  years  Paris  green  was 
practically  the  only  satisfactory  material  of  that  char- 
acter, and  even  that  could  not  be  used  on  tender  foliage 
or  on  conifers  without  extreme  caution.  Recently,  the 
manufacture  of  arsenate  of  lead  has  been  developed  to 
a  point  that  we  have  now  a  satisfactory  killing  agent 
that  can  be  safely  used  at  any  strength  on  foliage  of 
any  kind.  It  has  the  further  advantages  of  remaining 
well  in  suspension  without  constant  stirring,  and  of 
sticking  to  the  foliage  indefinitely  after  it  has  once 
dried.  In  the  garden  and  greenhouse  no  other  stomach 
poison  should  be  used  and  it  will  be  found  effective 
against  all  caterpillars,  saw-fly  slugs,  beetles  and  their 
larvae  and  generally  against  insects  that  actually  eat 
foliage;  it  is  useless  against  sucking  insects  such  as 
plant  lice,  scales,  plant  bugs  and  the  like.  It  contains 
less  actual  arsenic  than  Paris  green  and  at  least  three 
times  as  much  must  be  used  to  obtain  the  same  results. 
One  pound  in  10  gallons  of  water  will  kill  potato  beetles 
and  their  larvae;  i  pound  in  50  gallons  of  water  will 
kill  slugs  and  small  caterpillars;  i  pound  in  25  gallons 
of  water  is  a  good  general  strength  for  ordinary  cater- 
pillars and  other  similar  species.  Paris  green  is  perhaps 
a  little  more  economical  in  orchard  work  and  can  be 
used  at  the  rate  of  i  pound  in  50  gallons  of  water  for 
potato  beetles,  i  pound  in  125  gallons  for  orchard  work 
and  i  pound  in  150  gallons  on  sensitive  foliage  or  against 
young  caterpillars.  It  should  never  be  used  on  peach  or 
conifers  and  should  be  very  cautiously  used  in  the 
garden.  It  is  well  to  slack  one  pound  of  quick-lime 
with  every  pound  of  Paris  green  to  combine  all  the 
water-soluble  arsenic  in  the  insecticide,  especially  when 
used  at  the  greater  strengths. 


THE  WAR  ON  INSECTS  275 

Arsenate  of  lead  comes  in  paste  form  only,  at  present 
writing,  and  cannot  be  applied  dry.*  Paris  green  can  be 
mixed  with  air-slacked  lime  or  dry  hydrate  and  applied 
with  a  bellows,  and  for  cases  where  a  powdery  dusting 
will  form  as  satisfactory  a  coating  as  a  spray,  the  appli- 
cation in  that  manner  is  just  as  good.  There  are  cases, 
however,  as  where  an  insect  feeds  only  on  the  under- 
side of  a  leaf,  where  a  dust  does  not  and  cannot  cover  as 
well  as  a  spray,  and  others  where  the  material  must  be 
forcefully  applied  so  as  to  get  into  a  crevice  or  cavity 
in  order  to  secure  a  maximum  effect. 

There  are  preparations  of  white  arsenic  which  can  be 
made  at  home,  forming  combinations  with  lime  which 
are  stronger  and  cheaper  than  either  Paris  green  or 
arsenate  of  lead;  but  these  are  dangerous  in  unskilled 
hands  and  require  so  much  care  in  preparation  that 
they  are  not  advised,  save  when  very  large  quantities 
of  material  are  needed. 

It  is  very  often  desirable  to  combine  an  insecticide 
and  a  fungicide  so  as  to  prevent  injury  from  disease  as 
well  as  insects,  and  Bordeaux  mixture  is  the  fungicide 
generally  used  with  either  Paris  green  or  arsenate  of 
lead.  This  Bordeaux  mixture  is  in  itself  very  offensive 
to  many  insects  and  some  of  the  flea  beetles  will  scarcely 
touch  a  plant  protected  by  it.  If  the  arsenical  insecti- 
cide is  added  to  the  fungicide  in  the  same  proportion 
as  if  it  were  water,  an  extremely  effective  material  is 
obtained.  The  Bordeaux  mixture  is  prepared  as  follows: 

Copper  sulphate 4  pounds 

Quick-lime,  stone  or  shell,  good  quality  ....     4  pounds 
Water 50  gallons 

Dissolve  the  copper  sulphate  in  one  gallon  of  hot 
water,  slack  the  lime  in  water  sufficient  to  do  it  well, 
and  strain.  These  are  the  stock  mixtures  and  will 

*  A  dry  powder  has  been  produced,  but  is  still  in  the  experimental  stage. 


276  INSECTS 

keep  a  long  time  if  tightly  covered.  To  prepare  for  use 
dilute  each  of  the  stock  mixtures  with  ten  gallons  of 
water,  combine  them  in  a  barrel  of  sufficient  size,  and 
then  add  water  to  make  up  the  full  amount.  Never 
combine  the  concentrated  stock  mixtures  as  it  pro- 
duces a  heavy  coarse  precipitate  that  is  much  less 
effective.  The  above  mixture  is  the  full  strength  that 
is  reasonably  safe  for  general  use.  The  tendency  is  to 
use  only  three  pounds  of  copper  instead  of  four  on 
orchard  trees,  and  on  peach  it  should  be  even  weaker, 
if  used  at  all. 

Against  plant  lice,  scale  insects  and  other  sucking 
insects  our  battery  is  much  larger,  much  less  satisfac- 
tory, and  applications  must  be  much  more  carefully 
made.  We  can  spray  a  tree  with  arsenate  of  lead  to 
reach  an  insect  which  we  expect  will  make  its  appear- 
ance to-morrow;  but  a  contact  insecticide  must  be 
applied  when  the  insects  are  actually  present  and  must 
be  brought  into  actual  touch  with  the  specimen  before 
it  can  be  effective. 

Contact  poisons  kill  either  by  direct  corrosive  action 
on  the  skin  of  the  insect,  as  where  dry  hydrate  of  lime 
is  dusted  on  a  soft  slug,  or  by  clogging  or  entering  the 
body  through  the  spiracles  or  breathing  pores.  Soap 
mixtures  clog  by  forming  a  film  over  the  openings  and 
matting  up  the  hairy  guards  that  as  a  rule  protect 
them;  a  soap  that  makes  a  rather  thick  slimy  suds  is 
therefore  preferable  to  one  that  forms  a  clean,  thin 
suds.  Mineral  oils  are  very  penetrating  and  kill  by 
getting  into  the  body  cavity  through  all  openings. 
Decoctions  like  those  of  tobacco  and  hellebore  get  into 
the  spiracles  and  perhaps  also  through  the  mouth  into 
the  stomach  and  set  up  a  convulsive  affection  that  re- 
sults in  death.  Dry  powders  like  hellebore  and  tobacco 
are  effective  in  proportion  as  they  are  finely  ground,  and 


THE  WAR  ON  INSECTS  277 

even  fine  road  dust  has  some  insecticide  value.  The 
fine  dust  particles  get  into  the  trachea  and  there  set  up 
specific  irritation,  but  they  must  get  there  to  do  any 
good  at  all.  Coarse  particles  are  no  better  than  so 
much  coarse  dust  and  insects  with  covered  spiracles  are 
not  affected  at  all.  It  is  quite  possible,  therefore,  to 
have  an  insecticide  which  is  very  effective  against  one 
series  of  a  species,  but  which,  against  another  series, 
will  be  entirely  useless:  any  material  for  which  it  is 
claimed  that  it  will  kill  everything,  should  for  this 
reason  be  looked  upon  with  distrust  from  the  start. 

Plant  lice  are  among  the  most  common  of  all  the 
insects  to  be  dealt  with  in  a  practical  way,  because 
there  is  almost  no  vegetation  not  more  or  less  infested 
by  them.  In  a  small  way  on  house  plants,  insect  powder, 
i.e.,  pyrethrum,  is  the  cleanest  and  simplest  remedy. 
It  can  be  dusted  on  through  a  sieve,  put  on  with  a  little 
powder  puff  or  bellows,  or  it  can  be  made  into  a  decoc- 
tion or  tea,  using  an  ounce  to  two  quarts  of  hot  water. 
This  can  be  put  on  with  an  atomizer  and,  when  fresh,  it 
is  very  effective  against  all  kinds  of  plant  lice,  against 
most  small  caterpillars  and  slugs,  and  against  the 
larvae  of  scale  insects.  It  loses  strength  rapidly  when 
exposed  to  the  air,  and  in  corked  bottles  the  decoction 
ferments  and  moulds  after  a  day  or  two.  It  is  alto- 
gether too  expensive  for  general  use  in  fields,  but  in 
gardens  or  greenhouses  its  cleanliness  and  absolute 
safety  to  plants  are  in  its  favor. 

Tobacco  has  a  much  greater  range  of  usefulness. 
When  very  finely  powdered  it  may  be  dusted  on  and 
will  kill  about  the  same  sorts  of  insects  as  the  pyre- 
thrum.  It  may  be  worked  into  the  soil  of  pots  and 
benches  to  kill  root  lice,  besides  discouraging  many 
other  underground  insects.  It  is  also  a  fertilizer  and 
stimulates  the  plants  to  which  it  is  applied.  If  a  spray 


278  INSECTS 

is  preferred,  one  pound  of  chopped  tobacco  stems  may 
be  boiled  in  one  gallon  of  water  until  a  dark  brown 
extract  is  obtained,  and  this  will  control  white  fly, 
mealy  bugs  and  most  of  the  other  greenhouse  pests, 
provided  it  be  frequently  and  thoroughly  applied.  It 
stains  delicate  flowers  and  is  apt  to  cause  a  little  injury 
to  very  delicate  foliage,  but  in  general  it  is  safe  on  all 
ordinary  plants.  The  cost  of  tobacco  dust  or  ground 
tobacco  is  low  enough  to  warrant  its  use  in  gardens 
and  fields,  and  we  have  no  better  remedy  for  root  lice 
on  trees  and  plants;  even  the  woolly  apple  louse  suc- 
cumbs to  a  liberal  application.  To  reach  such  insects, 
the  soil  must  be  removed  to  a  depth  of  at  least  six 
inches  in  a  circle  from  eighteen  to  twenty-four  inches 
around  the  trunk,  varying  according  to  the  size  of  the 
tree,  before  a  layer  of  ground  tobacco  is  put  on,  and  the 
trench  must  be  then  filled  up.  The  soil  moisture  and 
rains  extract  the  nicotine  and  bring  it  into  contact 
with  the  root  lice.  Stems,  whole  or  coarsely  chopped, 
are  of  very  little  use,  since  the  nicotine  is  extracted  so 
slowly  as  to  be  ineffective.  Tobacco  is  also  used  in 
greenhouses  as  a  fumigant  and  is  quite  effective  against 
a  great  variety  of  pests.  It  may  be  burnt  on  a  layer  of 
hot  coal  in  an  open  stove,  an  extract  may  be  smeared 
on  the  pipes  for  slow  evaporation,  or  paper-rolls  soaked 
in  the  extract  may  be  burnt  on  wires  suspended  in 
different  parts  of  the  house.  And  that  brings  up  the 
point  that  there  are  now  on  the  market  commercial 
extracts  under  various  names  which,  when  only  small 
quantities  are  to  be  used,  are  cheaper  and  better  than 
can  be  made  at  home.  They  must,  however,  as  a  rule 
be  used  at  greater  strength  than  recommended  on  the 
labels  in  order  to  be  thoroughly  effective. 

Soaps   are   also   used   against   plant   lice   and   other 
sucking  insects  and  these  have  a  much  greater  range  of 


THE  WAR  ON  INSECTS  279 

effectiveness  than  the  extracts  just  mentioned  because 
of  their  greater  penetrating  power.  All  soaps  have 
some  insecticide  value,  and  so  washing  the  leaves  of 
house  plants  with  soapsuds  is  always  good  practice 
provided  the  suds  be  not  too  strong.  An  ounce  of  soap 
to  one  quart  of  water  is  ordinarily  quite  sufficient  to 
kill  green  lice  and  young  scales,  especially  if  whale  oil 
soap  is  used.  At  twice  that  strength  it  kills  even  the 
more  resistant  forms  of  plant  lice,  but  becomes  danger- 
ous on  tender  plant  foliage.  While  soapsuds  may  be 
freely  used  on  house  plants,  the  suds  should  not  be 
allowed  to  accumulate  on  the  surface  of  the  soil  for  the 
alkali  may  easily  become  detrimental  to  the  plant  roots. 
For  greenhouse  and  garden  use,  whale  oil  soap  is  much 
improved  by  an  addition  of  tobacco  and  such  a  combi- 
nation is  now  obtainable  from  most  seedsmen. 

In  the  field,  whale  oil  soap  is  much  used  against 
plant  lice,  and  is  effective  at  varying  strengths  de- 
pending on  the  insects  to  be  reached.  Against  most 
green  lice  i  pound  to  4  or  even  6  gallons  of  water  may 
be  satisfactory;  against  brown  or  black  Aphids  twice 
that  strength  may  be  required,  and  against  young  scales 
i  pound  in  2  gallons  is  the  weakest  mixture  that  can  be 
effectively  used.  For  winter  work  against  armored 
scales  like  the  San  Jose',  2  pounds  in  i  gallon  of  water 
are  applied. 

In  all  dealings  with  plant  lice  and  similar  insects 
that  multiply  rapidly,  prompt  action  is  essential  for 
best  results.  It  is  sometimes  easy  to  destroy  a  slight 
infestation  and  to  get  rid  of  a  few  specimens  on  leaves  or 
stems.  If  they  are  allowed  to  multiply  unchecked 
until  the  plant  begins  to  show  signs  of  suffering,  it  will 
be  necessary  to  make  much  more  thorough  treatments, 
and  as  many  species  tend  to  curl  or  otherwise  to  dis- 
tort the  leaves,  hiding  in  the  shelter  thus  caused,  it 


280  INSECTS 

becomes  also  more  difficult  to  reach  them.  It  must 
always  be  remembered  that  no  contact  poison  can  be 
effective  unless  it  actually  touches  the  insect  aimed  at, 
and  covering  the  top  of  a  leaf  no  matter  how  thoroughly, 
when  the  insects  are  feeding  on  the  underside,  is  of 
little  or  no  use.  More  ill  success  results  from  a  failure 
to  recognize  this  fact,  than  from  any  deficiency  in  the 
material  applied. 

There  are  a  large  number  of  "patented"  or  pro- 
prietary insecticides  on  the  market  for  killing  plant 
lice,  scales  and  similar  insects,  and  some  of  these  are 
really  meritorious;  but  they  are  usually  expensive  and, 
in  the  long  run,  no  better  than  the  materials  we  have 
just  enumerated. 

While  it  is  comparatively  easy  to  reach  and  control 
plant  lice  on  most  ordinary  farm  crops  and  in  the 
garden,  it  is  decidedly  more  difficult  to  reach  scales 
whether  soft  or  armored,  and  even  mealy  bugs  are 
difficult  to  kill,  in  spite  of  the  fact  that  they  are  com- 
paratively unprotected. 

There  is  only  one  period  in  the  life  of  such  insects 
when  they  are  within  reach  of  mild  applications  and 
that  is  when  the  young  have  just  hatched  and  are 
moving  about  without  protective  covering.  Theoreti- 
cally that  is  the  best  time  to  reach  them  and  with  some 
species  it  is  practically  the  only  time.  The  oyster 
shell  scales  and  some  others  that  attack  our  trees  and 
shrubs  winter  in  the  egg  stage  under  the  mother  scale, 
practically  safe  from  all  our  known  mixtures.  Early 
in  the  season,  depending  of  course  on  latitude  as  to  the 
exact  time,  these  eggs  hatch,  all  at  about  the  same  time, 
so  that  for  two  or  three  days  there  is  a  great  swarm  of 
naked  larvae,  and  for  a  week  there  are  newly  set  scales 
with  the  thinnest  sort  of  protective  covering;  that  is 
the  time  for  whale  oil  soap,  kerosene  emulsion,  miscible 


THE  WAR  ON  INSECTS  281 

oils  or  whatever  else  is  depended  upon  to  reach  the 
insects.  After  the  scale  has  once  hardened,  none  of 
our  summer  applications  that  are  safe  on  foliage  can  be 
relied  upon  to  kill.  A  large  number  of  scales,  soft  as 
well  as  armored,  come  under  this  general  rule  as  to 
development  and  treatment,  and  the  gardener  or  farmer 
who  has  insects  of  this  kind  to  deal  with,  should  know 
their  life  cycle  sufficiently  well  to  know  when  to  make 
his  applications. 

Scales  that  bear  living  young  usually  winter  in  the 
partly  grown  condition  and  may  be  reached  by  appli- 
cations which  either  penetrate  through  or  under  the 
protective  covering  to  the  insect  beneath.  When  repro- 
duction begins  the  larvae  are  born  singly,  a  few  each 
day,  and  this  may  continue  for  two  or  even  three  weeks. 
By  the  time  the  last  young  emerge,  the  earliest  are 
already  well  grown  and  covered  with  scales,  so  there  is 
no  time  when  a  single  application  will  reach  more  than 
a  small  proportion  of  the  infestation.  If  sprayings 
could  be  made  every  third  day  so  long  as  reproduction 
continues,  satisfactory  results  could  be  gotten;  but 
while  this  may  be  feasible  in  the  garden  and  green- 
house, it  is  not  practical  in  the  field  and  orchard.  In 
large  greenhouses  this  method  is  often  resorted  to  and 
the  scales  on  palms  and  other  hot-house  plants  are  kept 
under  control  by  frequent  application  of  weak  material. 

In  the  orchard  much  more  drastic  measures  must  be 
resorted  to,  and  in  winter  when  the  plants  are  dor- 
mant, very  caustic  or  very  penetrating  materials  are 
used.  For  caustics  nothing  is  much  better  or  more 
generally  effective  than  the  lime  and  sulphur  wash, 
formed  by  combining  one  pound  of  ground  or  flowers 
of  sulphur  with  one  pound  of  unslacked  stone  or  shell 
lime  in  three  gallons  of  water.  This  combination  is 
made  by  boiling  the  lime  and  sulphur  with  just  enough 


282  INSECTS 

water  to  do  it  properly  and  afterward  diluting  to  spray- 
ing strength.  It  usually  requires  about  one  hour's 
boiling  to  get  the  proper  combination  and,  when  re- 
duced with  warm  water  and  applied  fresh  on  peach 
and  plum  trees,  there  is  no  more  effective  remedy 
against  the  pernicious  or  San  Jos^  scale.  The  material 
is,  of  course,  quite  as  effective  a  killing  agent  on  other 
trees  as  well;  but  on  pear  and  apple  it  is  more  difficult 
to  reach  all  the  specimens  in  their  hiding  places  behind 
or  under  bud  or  bark  scales,  in  crevices  or,  in  the  case 
of  apples,  among  the  hairy  clothing  of  the  terminal 
shoots.  On  such  trees  the  wash  should  be  applied  with 
great  force  and  as  thin  as  possible  so  as  to  aid  its  pene- 
tration. On  peach,  plum  and  apricot  trees  it  exercises 
also  a  beneficial  effect  in  checking  certain  fungus  dis- 
eases and  improving  the  general  health  of  the  tree. 
On  trees  in  foliage  this  wash  should  never  be  used,  nor 
on  conifers  of  any  kind.  As  to  the  practical  work  of 
making  the  wash,  place  the  lime  and  the  sulphur  in  an 
iron  kettle  over  a  brisk  fire,  pour  in  hot  water  enough 
to  cover  and  start  slacking,  which  will  bring  the  mass  to 
the  boiling  point  at  once.  Add  hot  water  slowly,  stir- 
ring to  prevent  burning  and  to  facilitate  the  combination 
of  lime  and  sulphur.  One  part  of  good  lime  is  a  little 
more  than  enough  to  combine  one  part  equal  in  weight 
of  sulphur  and  any  excess  of  lime  remains  as  white- 
wash and  adds  nothing  to  the  effectiveness  of  the 
material.  If  the  lime  is  poor,  a  little  more  should  be 
used  to  make  sure  that  all  the  sulphur  is  combined. 
If  flowers  of  sulphur  are  used,  three-quarters  of  an 
hour's  boiling  is  sufficient  if  hot  water  is  used  as  a 
starter.  Otherwise  an  hour  is  better.  If  ground  sul- 
phur is  used  boil  half  an  hour  longer. 

Where  large  quantities  of  the  wash  are  to  be  made 
up,  live  steam  is  quite  generally  used,  and  the  mixture 


THE  WAR  ON  INSECTS  283 

is  made  in  barrels  into  which  live  steam  is  led  from  a 
central  boiler.  These  plants  vary  so  greatly  that  only 
the  principles  upon  which  they  are  built  can  be  stated. 
In  all  cases  there  is  a  drop  from  an  elevated  steam  pipe, 
reaching  to  the  bottom  of  the  barrel,  where  there  are 
usually  cross  arms  of  perforated  iron  pipe  to  permit 
the  steam  to  get  to  all  parts  of  the  mass  and  prevent 
irregular  cooking.  The  proper  amounts  of  lime,  sulphur 
and  water  are  put  into  the  barrel,  and  the  steam  is 
turned  on  for  an  hour  or  longer,  until  the  combination 
is  completed. 

It  is  also  possible  to  make  a  good  combination  of 
lime  and  sulphur  by  the  heat  of  slacking  lime  alone,  or 
by  using  potash  in  addition  to  the  lime  to  produce  the 
proper  degree  of  heat.  It  requires  heat  to  combine  the 
lime  and  sulphur  and  it  matters  little  whence  this  heat 
comes;  whether  from  burning  wood  or  coal,  from  steam, 
or  from  slacking  lime,  soda  or  potash.  The  wash  is 
effective  in  proportion  to  the  completeness  of  the 
combination  and  the  thoroughness  of  the  application. 

To  make  the  lime,  soda  and  sulphur  combination 
put  into  a  barrel  22  pounds  of  best  quality  stone  lime 
and  add  hot  water  enough  to  start  slacking.  While 
this  is  in  progress  sift  in  10  pounds  of  flowers  of  sul- 
phur, stirring  and  adding  hot  water  as  needed  until 
the  mass  is  well  reduced.  Then  add  n  pounds  more  of 
lime  with  more  hot  water,  and  sift  in  7  pounds  more  of 
sulphur  while  this  is  slacking.  Before  it  is  done  steam- 
ing, stir  in  ij  pounds  of  caustic  soda  which  will  cause  a 
violent  boiling,  and  when  this  begins  to  subside  add  an 
equal  amount  and  then  again  another  ij  pounds, 
making  4^  pounds  altogether.  Keep  stirring  and 
adding  hot  water  slowly  until  the  combination  is  com- 
pleted. Then  add  hot  water  to  make  50  gallons  and 
apply  at  once. 


284  INSECTS 

To  make  the  self-boiled  lime  and  sulphur  combina- 
tion, place  forty  pounds  of  best  quality  stone  lime  in  a 
barrel,  sifting  in  twenty  pounds  of  sulphur  flowers  with 
it  so  that  it  is  well  mingled.  Add  boiling  water  enough 
to  start  a  brisk  slacking  and  cover  with  a  heavy  blanket 
to  confine  the  heat.  Add  hot  water  as  needed  to  keep 
up  the  slacking,  and  stir  occasionally  to  aid  the  combi- 
nation. Keep  this  up  until  the  lime  is  fully  reduced  and 
mixed  with  the  sulphur.  Then  let  the  combination  stand 
covered  for  an  hour  to  maintain  its  heat,  after  which  hot 
water  enough  to  make  fifty  gallons  should  be  added. 

The  objection  to  these  mixtures  is  that  unless  they 
are  very  carefully  made  there  will  be  a  considerable 
percentage  of  uncombined  sulphur  which  is  of  no  value, 
and  there  is  so  great  an  excess  of  lime  forming  white- 
wash, that  it  makes  the  wash  too  thick  to  get  into 
crevices  or  through  plant  hairs.  But  even  this  wash  is 
now  made  commercially  and  there  are  several  brands 
on  the  market  which,  when  thinned  down  for  use,  cost 
very  little  more  than  the  home-made  wash,  and  much 
less  to  the  man  who  has  no  plant  available  for  making 
up  small  quantities.  Some  of  these  brands  have  been 
tried  in  comparison  with  the  home-made  wash  and, 
when  reduced  no  more  than  nine  times,  they  were 
quite  as  effective.  The  gardener  who  has  only  a  few 
trees  to  be  treated  will  save  time  and  money  by  using 
the  commercial  preparations. 

This  wash  is  extremely  caustic  and  corrosive.  Ma- 
chines in  which  it  has  been  used  should  be  thoroughly 
washed  out  and  oiled  before  being  put  away,  the  hands 
should  be  protected  by  gloves  while  spraying,  the  face 
should  have  a  coating  of  vaseline,  and  if  there  is  much 
wind  the  eyes  should  be  guarded  by  goggles. 

As  already  indicated  this  wash  was  developed  on 
the  Pacific  coast,  and  it  is  undoubtedly  more  uniformly 


THE  WAR  ON  INSECTS  285 

effective  there  than  it  is  on  the  Atlantic  coast.  A 
variety  of  reasons  for  this  difference  have  been  sug- 
gested, but  for  our  purpose  it  is  enough  to  recognize 
that  the  fact  exists. 

Sulphur  by  itself  is  not  a  mean  insecticide  if  we 
stretch  the  term  insect  just  a  little  so  as  to  include  the 
mites.  In  the  greenhouse,  against  red-spider  there  is 
nothing  much  better  than  flowers  of  sulphur  dusted  on 
the  surface,  where  the  slow  decomposition  generates 
fumes  that  are  fatal  to  the  mites  and  not  conducive 
to  the  multiplication  of  other  parasitic  organisms. 
In  the  citrus  orchards  of  Florida  a  similar  practice  is 
adopted  to  prevent  injury  from  the  rust  mite;  lump  or 
ground  sulphur  is  used,  and  here  the  hot,  moist 
atmosphere  favors  effects  that  are  unobtainable  in  the 
dry  climate  of  the  Pacific  Coast  regions. 

A  barrel  half  full  of  lump  sulphur  set  in  a  warm 
corner  of  the  greenhouse  and  kept  filled  with  water  is 
an  excellent  spraying  solution  for  general  use  on  the 
benches.  There  is  very  little  sulphur  in  the  solution, 
but  there  is  enough  to  keep  down  mites,  check  mildew 
and  destroy  many  other  spores  of  disease  organisms. 
As  the  water  is  used,  more  is  added,  so  that  half  a 
barrel  of  sulphur  may  last  a  year  or  more.  It  needs  a 
warm  corner  to  start  decomposition. 

Combined  in  a  soap,  sulphur  is  used  as  a  wash  for 
mangy  animals,  and  as  true  mange  is  due  to  a  mite, 
good  effects  are  obtained.  Better  yet  are  the  results 
when  sulphur  is  administered  internally.  It  is  one 
of  the  materials  eliminated  through  the  skin,  and  is 
therefore  brought  into  direct  contact  with  the  skin 
parasites. 

Among  the  penetrants  the  mineral  oils  rank  highest. 
A  light  crude  petroleum  of  the  paraffine  series,  testing 
43°  or  over  on  the  Beaume  scale,  will  penetrate  and 


286  INSECTS 

kill  every  scale  it  touches,  and  it  spreads  so  well  that  it 
will  get  under  every  protection,  into  every  crevice  and 
through  every  covering  of  plant  hairs.  Unfortunately 
it  goes  further  and,  if  carelessly  used,  is  just  as  likely 
to  get  through  the  outer  bark  into  the  bast,  and  to  kill 
the  tree  as  well  as  the  insect.  Nevertheless  the  material 
has  been  and  is  even  yet  quite  extensively  used,  and  is 
the  reliance  of  a  large  number  of  good  fruit-growers. 
I  do  not  advise  its  general  use,  but  mention  it  for  the 
benefit  of  those  willing  to  try  it.  In  the  garden  and 
conservatory  it  has  no  place. 

Kerosene  is  a  derivative  from  the  crude  petroleum, 
with  the  lighter  volatile  oils,  the  vaseline  and  the  par- 
amne  eliminated.  It  can  be  safely  applied  to  trees 
even  when  in  full  foliage,  in  a  very  fine  spray,  under 
conditions  which  favor  rapid  evaporation.  I  have 
frequently  applied  it  with  excellent  effect  late  in  summer 
on  very  scaly  trees,  killing  off  most  of  the  insects  with- 
out appreciable  harm  to  the  tree  itself.  Apple  and 
pear  trees  are  most  resistant  to  the  mineral  oils;  peach 
and  other  stone  fruits  are  most  susceptible.  Citrus 
trees  stand  kerosene  very  well  under  favorable  condi- 
tions; but  on  the  whole  this  is  another  material  which 
needs  a  thorough  appreciation  of  all  the  factors  in- 
volved to  make  it  safe.  As  a  winter  application  it  is 
not  nearly  so  effective  as  crude  oil  because  it  evapo- 
rates so  much  more  completely,  leaving  nothing  in  the 
way  of  a  coating  to  continue  its  work;  but  that  very 
feature  makes  it  safer  to  use. 

The  good  points  of  kerosene  as  an  insecticide  were 
long  ago  recognized,  and  nearly  thirty  years  ago  methods 
of  emulsifying  it  with  milk  and  afterward  with  soap 
were  worked  out  under  the  direction  of  Dr.  C.  V.  Riley 
then  U.  S.  entomologist,  by  Mr.  H.  G.  Hubbard.  The 
milk  formula  was  soon  abandoned;  but  the  soap  emul- 


THE  WAR  ON  INSECTS  287 

sion  stands  to  this  very  day,  much  the  same  as  Mr. 
Hubbard  worked  it  out. 

Kerosene 2  gallons 

Water i  gallon 

Hard  soap \  pound 

Shave  the  soap  fine  and  dissolve  in  boiling  water; 
warm  the  kerosene  and  add  to  the  boiling  suds;  churn 
with  a  force  pump  by  pumping  back  into  the  pail 
through  a  fine  nozzle  until  a  thick  white  cream  is  formed. 
This  hardens  into  a  butter-like  mass  when  cold  and 
may  be  diluted  to  any  desired  extent  with  water.  If 
both  kerosene  and  suds  are  hot,  five  minutes'  churning 
will  bring  the  proper  combination.  In  making  and 
diluting  the  emulsion,  soft  water  should  be  used  and 
only  a  little  water  should  be  mixed  in  at  first  to  get 
the  butter  into  soluble  form.  A  well-made  emulsion 
will  keep  for  weeks  in  a  dark  cool  place;  but  event- 
ually the  oil  will  separate  and  come  to  the  top. 

Diluted  with  from  twelve  to  fifteen  times  its  own 
bulk  of  water  this  is  an  excellent  summer  remedy  for 
plant  lice,  young  leaf -hoppers,  mites,  thrips  and  other 
insects  liable  to  be  killed  by  contact  poisons.  The  pene- 
trating qualities  of  the  oil  and  clogging  effect  of  the 
soap  are  combined;  but  the  soap  prevents  the  rapid 
evaporation  of  the  kerosene,  holds  it  longer  in  actual 
contact  with  the  vegetation  to  which  it  is  applied,  and 
thereby  increases  its  danger.  Most  plants  will  stand 
an  application  of  i  to  15;  few  plants  will  safely  stand 
anything  stronger  than  i  to  10,  and  i  to  12  is  the  more 
usual  limit.  As  a  summer  wash  against  scale  larvae 
the  i  to  10  mixture  is  an  excellent  combination  on  all 
save  stone  fruits,  and  even  i  to  15  must  be  carefully 
used  on  such.  For  winter  work  it  is  not  advised,  because 
at  a  dilution  strong  enough  to  kill  scales,  it  is  actually 


288  INSECTS 

more  dangerous  to  the  trees  than  the  undiluted  oil 
itself.  Nevertheless,  kerosene  emulsion  shares  with 
whale  oil  soap  the  burden  of  the  fight  against  plant  lice, 
with  the  advantage  of  cost  in  favor  of  the  emulsion. 

A  more  recent  development  in  the  use  of  petroleum 
oils  is  found  in  the  miscible  or  "soluble"  oils,  sold 
under  special  names  such  as  "Scalecide,"  "  Kill-O- 
Scale,"  "San-U-Zay,"  or  simply  as  "soluble  petro- 
leum." These  are  preparations  of  petroleum,  crude  or 
partly  refined,  so  combined  with  vegetable  or  animal 
oils,  rosin  oil  and  sulphonated  oil,  as  to  be  readily 
miscible  in  water  to  any  extent,  forming  a  perfectly 
homogeneous  spraying  mixture  of  even  effectiveness 
throughout.  None  of  these  oils  contain  over  75  per 
cent,  actual  petroleum  and  few  contain  over  10  per 
cent,  of  water,  which  is  actually  necessary  to  form  the 
emulsion.  They  are,  therefore,  approximately  equal 
in  their  effect  and  are  extremely  useful  as  winter  washes 
against  scales  hibernating  in  the  partly  grown  condi- 
tion. Against  the  pernicious  or  San  Jose  scale  a  dilu- 
tion with  fifteen  parts  of  water  is  the  weakest  mixture 
that  should  be  used  in  general  practice.  Good  results 
have  been  obtained  with  a  solution  of  20  to  i,  under 
exceptional  circumstances;  but  I  would  rather  recom- 
mend a  dilution  of  only  twelve  times  if  I  were  anxious 
to  secure  definite  effects.  These  oils  have  no  vaseline 
or  paraffin  e  residue,  hence  can  be  safely  applied  for 
successive  years,  even  peach  showing  no  appreciable 
injury  within  my  experience.  It  is  on  large  old  apple 
and  pear  trees  that  these  miscible  oils  find  their  most 
effective  field  of  use,  for  they  spread  and  penetrate 
well  and  when  applied  with  proper  force  can  be  made 
to  reach  wherever  a  scale  can  go.  This  quality  makes 
them  effective  against  such  species  as  the  pear  psylla, 
which  hibernate  as  adults  in  crevices  and  under  rough 


THE  WAR  ON  INSECTS  289 

bark  scales,  and  against  such  mites  as  hibernate  under 
bud  scales  or  in  similar  positions.  They  are  not  espe- 
cially effective  against  insect  eggs,  and  have  little 
fungicidal  value.  In  all  cases  where  the  oils  and  the 
lime  and  sulphur  are  equally  effective,  the  latter  is 
preferable  because  of  its  influence  on  plant  diseases. 
"Soluble"  oils  are  not  safe  as  summer  washes  at  effec- 
tive strengths,  although  when  carefully  applied  on 
mature  foliage  of  hardy  trees,  no  serious  injury  is  caused. 

Miscible  oils  can  be  made  at  home  and  formulas 
have  been  published  minutely  describing  the  process; 
but  it  requires  skill,  absolutely  uniform  materials  and 
an  outfit  that  only  the  user  of  large  quantities  can 
afford.  Furthermore  it  is  an  unpleasant  and  even 
somewhat  dangerous  process  which  can  hardly  be 
recommended  to  ordinary  farmers  and  fruit-growers, 
and  certainly  not  to  gardeners  using  only  a  few  gallons 
or  even  barrels. 

There  is  another  field  for  kerosene  emulsion  and  the 
like  when  it  is  necessary  to  reach  certain  leaf-miners 
which,  while  feeding  on  plant  tissue  are  never  exposed 
to  the  action  <of  arsenical  coverings,  but  live  entirely  in 
the  leaf  tissue.  There  is  usually,  however,  an  opening 
to  the  surface,  or  the  tissue  above  the  mine  is  so  thin 
as  to  be  readily  penetrated  by  the  oil;  hence  a  contact 
insecticide  against  a  leaf-miner  is  indicated. 

It  is  with  the  mineral  oils  as  with  the  lime  and 
sulphur;  the  effects  are  not  equally  satisfactory  under 
all  climatic  conditions.  Applications  that  are  entirely 
safe  in  one  locality  may  be  distinctly  injurious  to  plants 
in  another,  and  a  little  caution  must  be  observed  when 
the  material  is  used  for  the  first  time  in  localities  differ- 
ing from  those  in  which  it  has  been  tested. 

Another  combination  with  both  caustic  and  pene- 
trating qualities  as  well  as  a  specific  feature  of  its  own 


290  INSECTS 

is  found  in  the  resin  washes  which  have  had  a  wide  use 
on  the  Pacific  coast,  but  have  not  been  much  exploited 
in  the  east.  Two  formulas  for  summer  and  winter 
washes  are  given: 

SUMMER  FORMULA. 

Resin 20  pounds 

Caustic  soda,  70  per  cent,  or  over 5  pounds 

Fish  oil 3  pints 

Water  sufficient  to  make 100  gallons 

WINTER  FORMULA. 

Resin 30  pounds 

Caustic  soda,  70  per  cent,  or  over 9  pounds 

Fish  oil 4$  pints 

Water  sufficient  to  make i  oo  gallons 

These  are  really  very  thin  varnishes,  readily  soluble 
in  water  and  therefore  more  effective  in  a  dry  climate. 
The  second  or  winter  wash  contains  so  much  resin  that 
its  application  to  foliage  would  choke  and  thus  destroy 
it  and  is  also  much  more  caustic.  The  summer  wash  is 
effective  against  scale  larvae,  recent  sets,  plant  lice  and 
similar  species,  clogging  their  spiracles. 

To  make  these  washes,  boil  all  the  ingredients 
together  with  about  twenty  gallons  of  water  until 
thoroughly  dissolved,  adding  hot  water  from  time  to 
time  as  needed,  but  never  enough  to  stop  the  boiling 
after  it  has  once  begun.  Three  hours  will  be  required 
for  a  complete  mixture,  hot  water  being  gradually 
added  to  make  up  fifty  gallons,  stirring  continuously. 
After  this,  the  balance  of  the  100  gallons  may  be  added 
in  cold  water.  It  may  be  that  the  work  of  preparing 
these  washes  has  something  to  do  with  their  present 
lack  of  popularity. 

It  frequently  happens  that  we  have  underground 
insects  such  as  root  maggots  to  deal  with,  and  none  of 
the  soap  or  petroleum  washes  heretofore  considered  is 


THE  WAR  ON  INSECTS  291 

of  any  value  in  this  direction.  The  petroleum  mixt- 
ures, indeed,  usually  kill  the  plants  primarily  and 
the  maggots  consequentially.  We  derive  some  help 
from  carbolic  acid  emulsified  with  soap,  so  as  to  be 
soluble  in  water.  To  make  this,  dissolve  one  pound  of 
hard  soap  shaved  fine,  in  one  gallon  of  boiling  water, 
add  one  pint  of  crude  carbolic  acid  (50  per  cent.),  and 
churn  the  whole  into  an  emulsion  with  a  force  pump. 
This  emulsion  is  diluted  for  use  with  thirty  times  its 
own  bulk  of  water,  and  applied  to  the  soil  at  the  base  of 
infested  plants.  The  mixture,  to  be  effective,  must 
come  into  direct  contact  with  the  insects,  hence  the 
earlier  it  is  applied  when  cabbages  and  onions  are 
infested,  the  more  effective  it  will  be;  there  must  be 
enough  material  to  penetrate  down  to  the  lowest  point 
reached  by  the  maggots.  On  cabbages  this  may  be 
three  or  even  four  inches  and  may  require  half  a  pint  of 
material;  on  onions  it  would  not  be  over  an  inch  or 
two,  and  would  of  course  require  much  less.  Wire- 
worms  and  white  grubs  are  also  affected  by  this  emul- 
sion and  driven  away  or  killed.  On  growing  foliage  it 
cannot  be  safely  applied,  and  it  is  unsuitable  for  use 
against  maggots  infesting  radishes  or  beets. 

Carbolic  acid  is  sometimes  used  to  increase  the 
effectiveness  of  whale  oil  soap  and  an  ounce  of  the 
acid  in  a  gallon  of  spray  mixture  does  improve  it  to 
some  extent,  but  not  enough  to  balance  the  extra  cost 
and  labor  of  working  it  in.  It  has  been  added  to  air- 
slacked  lime  for  use  as  a  repellent  around  melon  and 
other  cucurbit  vines  to  keep  off  the  melon  beetles.  It 
forms  an  ingredient  in  tree  washes  and  preparations 
intended  to  prevent  the  entrance  of  borers,  and  is 
somewhat  effective  in  this  direction.  But  insects  are 
not  often  adversely  affected  by  unpleasant  odors  unless 
they  are  also  directly  poisonous. 


292  INSECTS 

Another  use  that  has  been  proposed  for  the  acid  is 
to  paint  a  band  around  the  trunks  of  fruit  trees  with 
the  idea  that  it  would  be  absorbed  by  the  bark  and 
carried  into  the  circulation,  poisoning  the  sap  to  such 
an  extent  as  to  kill  all  the  scales  and  other  insects  feed- 
ing on  the  tree.  The  theory  is  a  very  plausible  one  at 
first  sight,  but  unfortunately  the  acid  as  it  penetrates 
strikes  first  the  down-current  that  carries  it  to  the 
roots,  and  when  there  is  enough  of  it  to  get  into  the 
active  cells,  these  promptly  die  and  refuse  to  do  any 
carrying.  If  the  acid  gets  still  further  and  really  does 
strike  the  up-current,  then  the  girdling  is  complete 
and  the  tree  itself  dies.  Rarely,  however,  is  there 
enough  acid  applied  to  cause  this  mischief. 

This  suggests  the  fact  that  there  are  always  a  num- 
ber of  philanthropic  gentlemen  ready  to  aid  the  farmer 
— for  a  consideration — and  willing  to  insert  into  his 
trees  a  compound  of  which  they  only  possess  the  secret, 
which  will  infallibly  kill  all  the  insects  infesting  the  tree 
and  cure  all  its  diseases.  They  are  even  willing  to  give 
a  written  guarantee  to  that  effect.  Many  a  farmer 
and  tree  owner  even  in  cities  and  towns  falls  victim 
to  the  persuasiveness  of  these  benefactors,  who  bore 
holes  two  inches  deep  into  the  wood,  fill  them  with 
their  compound  and  fasten  it  in  tightly  with  a  wooden 
plug,  absolutely  beyond  reach  of  those  cells  of  the 
tree  engaged  in  carrying  sap.  Even  were  the  material 
soluble  and  active,  it  is  imbedded  in  tissue  which  serves 
only  as  a  support  to  the  tree,  and  has  absolutely  nothing 
to  do  with  its  nourishment.  Its  absorption  into  the 
surrounding  cells  would  therefore  mean  precisely  as 
much  as  if  it  were  absorbed  into  the  tissues  of  the 
nearest  fence  or  hitching  post. 

Caustic  potash  and  caustic  soda  have  a  limited  use 
on  the  farm,  but  in  the  orchard  and  garden  are  fre- 


THE  WAR  ON  INSECTS  293 

quently  used  as  winter  washes  for  tree  trunks.  In  a 
solution  of  one  pound  in  one  gallon  of  water  we  have. a 
mixture  which  kills  lichens  and  mosses  on  tree  trunks 
as  well  as  many  spores  of  fungi,  and  leaves  the  bark 
in  a  nice,  clean,  shining  condition,  vigorous  and  free 
from  all  clogging  organisms.  It  is  astonishing  what  an 
improvement  a  wash  of  this  kind  will  often  produce  on 
fruit  and  shade  trees,  and  where  a  clean  healthy  bark 
is  a  desideratum,  there  is  no  better  way  to  obtain  it. 
Besides  cleaning  the  bark,  this  material  will  also  corrode 
and  destroy  many  of  the  thinner  scales  such  as  the 
species  of  Chionaspis  of  which  the  scurfy  scale  is  an 
example.  That  species  hibernates  in  the  egg  state,  and 
the  egg  is  not  affected  by  the  caustic;  but  the  scale 
covering  is  thin,  easily  corroded,  and  the  eggs  are  then 
washed  out  and  scattered  by  rains.  Those  larvae  that 
hatch  from  them  will  rarely  be  able  to  find  their  way 
back  to  the  tree,  and  in  most  instances  the  eggs  them- 
selves perish  under  the  unnatural  conditions.  A  ma- 
terial so  caustic  as  this  should  be  carefully  handled, 
for  sores  caused  by  it  frequently  ulcerate  badly  and 
heal  very  slowly,  because  of  the  destruction  of  tissue. 

Lime  is  one  of  the  most  useful  materials  on  the 
farm  from  a  great  many  points  of  view.  Few  insects 
care  to  rest  voluntarily  on  a  lime-covered  surface; 
only  hunger  will  induce  most  species  to  eat  through  it, 
and  some  will  not  touch  it  under  any  circumstances. 
Lime  in  its  various  forms  is  about  the  only  material 
used  by  most  European  orchardists,  and  whitewashed 
trees  form  a  characteristic  feature  in  many  localities. 
As  a  whitewash  on  fences  and  farm  buildings  generally, 
inside  and  out,  it  covers  over  or  fills  crevices  and  cavi- 
ties that  would  otherwise  serve  as  hiding  places  for 
insects.  It  seals  up  and  destroys  the  eggs  of  such  insects 
as  may  be  present  when  the  wash  is  applied,  and  on 


294  INSECTS 

tree  trunks  it  prevents  the  setting  of  young  scales.  A 
continuous  coat  of  whitewash  will  absolutely  prevent 
the  setting  of  all  scales  and  will  keep  many  of  them 
from  hatching;  but  it  requires  rather  a  thick  coating  to 
effect  this,  for  the  lifting  of  the  scales  when  the  young 
are  ready  to  emerge,  will  usually  break  the  coating. 
In  chicken-houses  the  wash  should  be  applied  with  a 
spray  pump  so  as  to  force  it  into  cracks  and  crevices, 
and  the  addition  of  a  little  carbolic  acid  is  here  a  dis- 
tinct gain  to  the  wash.  The  same  may  be  said  of  it  in 
stables  and  out-buildings  generally.  Instead  of  the 
crude  carbolic  acid,  which  is  not  readily  soluble  or  mis- 
cible  with  watery  liquids,  one  of  the  many  soluble  tar 
or  cresol  preparations  may  be  used  in  liberal  quantities. 
Tree  trunks  are  often  white-washed  to  prevent  borers 
from  entering,  and  with  good  effect  so  long  as  the 
coating  is  thick  and  well  put  on.  But  the  egg-laying 
instinct  is  among  the  strongest,  and  the  parent  beetles 
of  round,  flat-headed  and  bark  borers  will  hunt  for  a 
broken  point,  an  unfilled  crevice  or  a  loosened  bark 
scale,  to  find  a  place  where  they  can  safely  deposit  an 
egg,  while  the  clear-wing  moths  will  lay  their  eggs 
anyway,  and  trust  the  minute  caterpillar  to  find' a  bare 
place  or  a  crevice  through  which  entrance  may  be 
obtained  to  the  sap-wood  below. 

On  foliage,  whitewash  is  not  an  advisable  applica- 
tion; its  brittle  character  makes  it  quickly  imperfect, 
even  where  the  tissue  itself  is  not  harmed. 

In  its  dry  condition  the  range  of  usefulness  of  lime 
is  much  greater.  Air-slacked  lime  mixed  with  Paris 
green  for  application  through  a  blower  or  powder  bel- 
lows is  well  known,  and  as  a  driver  in  fields  of  cucurbs 
invaded  by  the  cucumber  beetles,  it  is  relied  upon  in 
many  parts  of  the  country.  As  a  dry  hydrate,  that  is 
slacked  with  just  enough  water  to  crumble  it  into  a  dry 


THE  WAR  ON  INSECTS  295 

powder,  it  is  useful  against  a  great  variety  of  viscid  or 
moist  slugs,  like  those  of  the  asparagus,  potato,  pear  and 
the  like.  When  slacked  in  this  way  the  fine  particles  of 
lime  are  still  very  caustic  and  need  another  particle  of 
water  to  complete  the  slacking.  If,  in  this  condition,  the 
lime  is  dusted  on  the  moist  slugs,  each  particle  of  lime 
gets  the  desired  particle  of  water  from  the  body  of  the 
slug,  and  in  doing  so  burns  a  little  hole  into  the  skin. 
The  effectiveness  of  a  dry  lime  application,  therefore, 
depends  on  the  moist  condition  of  the  insect  to  be 
dealt  with,  and  in  consequence  early  morning  appli- 
cations when  there  is  a  little  dew  are  always  most 
effective.  In  the  asparagus  fields  where  once  the  slugs 
have  gotten  a  start  after  the  cutting  season  is  over, 
there  is  nothing  better  than  a  cloud  of  dry  hydrate  of 
lime  put  on  with  a  powder  gun  just  at  sunrise  or  a  little 
before. 

This  reference  to  the  time  of  application  in  order  to 
reach  the  insects  in  the  best  condition  brings  to  mind 
that  there  are  some  plants  and  insects  that  by  reason 
of  a  waxy  or  powdery  surface  or  covering  repel  or  shed 
water  particles.  The  woolly  lice  and  mealy  bugs  are 
insect  examples  and  the  cabbage  leaves  are  good  plant 
examples.  When  cabbage  plants  are  attacked  by 
Aphids  which  have  a  covering  of  fine  waxy  powder, 
ordinary  watery  applications  are  of  little  or  no  use, 
and  even  soap  washes  or  kerosene  emulsions  must  be 
applied  with  considerable  force  and  in  a  fine  spray  to 
really  wet  and  be  effective.  When  on  cabbage  or  simi- 
lar plants  arsenical  applications  are  required,  the 
matter  becomes  even  more  difficult  and  some  sort  of 
adhesive  is  needed.  Molasses,  glucose  and  soap  add 
materially  to  the  sticking  qualities  of  arsenical  sprays 
other  than  arsenate  of  lead;  but  in  extreme  cases  a 
resin  soap  is  needed.  Such  resin  soap  may  be  pur- 


296  INSECTS 

chased,  or  may  be  made  up  according  to  the  following 
formula: 

Pulverized  resin 5  pounds 

Concentrated  lye i  pound 

Fish  oil i  pint 

Water 5  gallons 

Boil  resin  and  oil  in  one  gallon  of  water  until  the 
resin  is  thoroughly  softened,  then  dissolve  and  add  the 
lye  slowly,  stirring  continuously  until  thoroughly  mixed. 
Then  add  four  gallons  of  water  and  boil  for  about  two 
hours  or  until  you  get  a  clear  amber-colored  liquid  which 
dissolves  readily  in  cold  water.  This  liquid  resin  soap 
may  be  added  at  the  rate  of  one  gallon  to  every  100 
gallons  of  any  arsenical  spraying  mixture  other  than 
arsenate  of  lead,  or  at  the  rate  of  one  gallon  for  every 
fifty  gallons  of  any  spray  used  on  cabbage  or  similar 
waxy  leaves.  The  adhesive  should  be  placed  in  the 
entire  amount  of  water  to  be  used  and,  when  thor- 
oughly dissolved,  the  Paris  green  or  other  poison  should 
be  added. 

Powdered  white  hellebore  was  at  one  time  almost 
the  main  reliance  against  saw-fly  larvae  such  as  the 
currant  worm,  and  is  even  yet  the  •  favorite  for  this 
purpose  with  many  gardeners.  It  may  be  applied  as  a 
dry  powder,  pure  or  mixed  with  two  or  three  times  its 
own  weight  of  cheap  flour;  or  it  may  be  used  in  the 
form  of  a  decoction,  using  one  ounce,  steeped  in  two 
quarts  of  hot  water.  This  is  also  effective  against 
certain  small  caterpillars  and  naked  slugs,  but  is  not  so 
reliable  and  is  more  expensive  than  some  of  the  other 
materials  already  recommended. 

Sometimes  we  can  make  use  of  certain  abnormal 
tastes  among  insects  to  secure  their  destruction.  Thus 
cut- worms  prefer  wheat  bran  to  their  normal  food, 


THE  WAR  ON  INSECTS  297 

and  will  eat  it  by  choice  even  when  a  corn  plant  grows 
near  by.  We  take  advantage  of  this  habit  by  making 
up  a  mixture  of  white  arsenic  one  pound,  to  wheat 
bran  seventy-five  pounds;  mingle  thoroughly,  moisten 
with  sugar  water  enough  to  make  a  soft  mush  and  put  a 
spoonful  in  the  hill  of  plants  to  be  protected.  There 
will  be  dead  cut-worms  next  morning,  and  no  further 
cutting  of  plants.  Sometimes,  where  a  field  of  grass 
has  been  plowed  down  and  cut-worms  are  known  to  be 
present,  rows  of  the  dry  bran  and  arsenate  mixture  are 
drilled  at  ten-foot  intervals  across  the  field  to  attract 
and  destroy  the  worms  before  the  crop  is  set  out  or  is 
up,  as  the  case  may  be.  Paris  green  may  be  used  in- 
stead of  arsenic,  but  the  latter  is  cheaper.  Chickens  or 
other  farm  animals  liable  to  eat  this  poisoned  bran 
should  of  course  be  kept  out  of  fields  so  treated. 

Grasshoppers  of  certain  injurious  species  have  an 
abnormal  fondness  for  moist  horse  manure  and  great 
numbers  can  be  killed  off  by  mixing  one  pound  of 
arsenic  with  three  gallons  of  droppings  and  spreading 
where  the  insects  are  most  numerous.  It  is  better  to 
use  small  quantities  several  days  in  succession  than 
large  quantities  at  one  time,  because  as  the  material 
dries  out  it  loses  its  attraction. 

To  keep  borers  out  of  fruit  and  shade  trees,  all  sorts 
of  mechanical  protections  have  been  devised.  The  use 
of  lime-wash  has  been  already  referred  to,  and  that  is 
most  wide-spread.  Sometimes  soap,  carbolic  acid  and 
arsenic  are  added,  and  help  a  little  toward  its  effective- 
ness, because  the  poison  may  kill  the  parent  beetles 
when  cutting  a  place  for  the  egg,  or  the  young  larvae 
when  attempting  to  enter.  Sometimes  the  entire  trunk 
is  cased  in  wire  mosquito  netting  held  at  a  distance  of 
at  least  half  an  inch  from  the  bark  at  all  points,  and 
sometimes  only  the  lower  portion  of  the  trunk  is  so 


298  INSECTS 

protected.  The  round-headed  borers  of  pomaceous 
fruits  like  apple  and  quince,  and  the  boring  caterpillars 
infesting  peach  and  its  allies,  usually  enter  near  the 
surface  and  work  in  just  at  or  below  the  ground.  A 
wTash  of  hydraulic  cement  mixed  with  water,  or  better, 
with  milk,  is  often  used  to  protect  trees  at  this  point 
and  on  peach  trees  a  band  of  newspaper  or  tar  paper  is 
tied  so  as  to  extend  a  little  below  the  surface  and  for  a 
distance  of  eighteen  inches  above.  Other  mixtures  have 
been  recommended  and  all  are  more  or  less  effective. 
It  means  simply  coating  the  bark  with  anything  that 
the  insects  cannot  or  will  not  penetrate  in  their  efforts 
to  get  to  their  place  of  feeding. 

Gas  tar  is  safely  used  in  some  localities  as  a  protec- 
tion, but  in  others  is  fatal  to  the  trees,  and  it  is  better 
not  to  use  tar  paper  or  any  black  paper,  since  that 
seems  to  cause  a  scalding  of  the  bark  beneath  it.  So, 
while  paints  mixed  with  linseed  oil  are  tolerably  safe, 
those  in  which  turpentine  is  used  should  be  avoided, 
as  they  are  almost  always  dangerous. 

A  great  variety  of  protective  devices  are  in  use  on 
trees  to  prevent  insects  from  getting  up  or  down  the 
trunk,  or  to  attract  them  as  shelter  for  larvae  and 
pupae,  and  some  of  these  are  effective  in  special  cases, 
as  when  a  band  of  fluffy  cotton  or  of  a  sticky  material 
bars  the  ascent  of  female  canker-worm  moths  or  the 
ascent  of  caterpillars  of  the  tussock  moths,  from  egg 
masses  laid  below  them.  The  larvae  of  codling  moths 
can  be  attracted  to  burlap  bands  when  they  leave  the 
fruits  to  pupate,  and  many  of  them  can  be  there  gathered 
and  destroyed.  Finally,  on  field  crops  we  can  use,  very 
effectively,  tar  paper  discs  to  protect  cabbage  plants 
from  root  maggots. 

The  direct  campaign  with  poisons  is  a  most  impor- 
tant feature  of  the  war  with  insects,  and  to  carry  it  on 


THE  WAR  ON  INSECTS  299 

we  need  a  great  variety  of  machinery  for  applying  pow- 
ders and  liquids,  and  such  machinery  is  now  obtainable 
almost  throughout  the  civilized  world,  to  meet  the  needs 
of  the  man  who  wishes  to  protect  one  plant  as  well  as  of 
him  who  farms  ten  thousand  acres.  There  is  every 
range  from  the  little  atomizer  to  the  steam  pump,  and 
from  the  little  powder  bellows  to  the  rotary  fan  blower 
capable  of  enveloping  a  large  tree  in  a  dust  cloud.  Spe- 
cific description  of  such  machinery  would  be  of  little 
avail,  and  he  who  has  the  selection  need  keep  in  mind 
only  a  few  fundamental  points.  The  apparatus  should 
be  so  simple  as  to  be  fully  understood  by  the  pur- 
chaser; it  should  be  well  made  and  of  the  most  durable 
material;  it  should  be  more  than  equal  to  the  utmost 
demands  ever  made  on  it;  it  should  be  able  to  give 
great  force  to  the  material  issuing  from  spout  or  nozzle, 
and  there  should  be  a  nozzle  or  spout  capable  of  bring- 
ing the  dust  or  liquid  into  actual  contact  with  all  the 
insects  to  be  reached,  under  all  the  circumstances 
under  which  they  occur.  Thoroughness  of  application 
is  always  essential  to  success,  and  careless  work  is  al- 
ways wasteful  and  expensive  work. 

We  are  not  confined  in  our  work  to  insecticides 
merely.  Modifications  of  the  primitive  method  of  col- 
lecting potato  beetles  in  tin  pans  with  a  scum  of  kero- 
sene are  still  in  use,  and  in  some  cases  form  our  only 
practical  line  of  offense.  Leaf -hoppers  and  grass- 
hoppers are  collected  by  means  of  hopper-dozers  drawn 
by  man  or  horse  power  over  infested  fields,  gathering 
up  the  insects  on  a  bed  of  soft  tar  or  petroleum.  We 
have  similar  contrivances  to  run  under  grape  vines 
into  which  we  jar  rose-chafers,  and  wheeled,  umbrella- 
like  structures  to  capture  plum  curculios.  In  a  few 
cases  when  large,  conspicuous  caterpillars  like  those  of 
the  hawk-moths  infest  low  plants  like  tobacco  or  toma- 


300  INSECTS 

toes,  hand  picking  is  the  best  and  most  reliable  method. 

So,  when  borers  get  into  our  peach  trees,  the  only 
really  effective  way  is  to  go  after  them  with  a  knife, 
and  if  apple  or  similar  round-headed  borers  are  in 
fault,  a  soft  wire  is  added  to  the  outfit  to  reach  such 
insects  as  have  gotten  into  the  heart  wood. 

Against  species  that  march  we  erect  barriers  of  one 
kind  or  another.  Army -worms  and  chinch-bugs,  for 
instance,  may  sometimes  be  stopped  by  running  a 
ditch  across  their  path  or  a  couple  of  plowed  furrows 
with  steep  sides  to  prevent  their  easy  ascent.  At 
intervals  in  these  furrows  post  holes  are  driven  and  as 
the  insects  crawl  along  the  bottom  of  the  furrow  or 
ditch  seeking  a  way  out,  they  fall  into  the  post  holes 
and  are  treated  to  a  dose  of  kerosene.  Myriads  of 
specimens  are  often  killed  off  in  such  campaigns,  and 
the  farmer  saves  his  crops,  without  perceptibly  de- 
creasing the  number  of  his  foes  for  the  year  to  come. 

Some  species  we  are  able  to  circumvent  by  a  little 
adaptation  of  our  farm  practice.  For  instance,  where 
corn  is  raised  continuously  on  the  same  land  in  the 
middle  west,  the  corn-root  worm  soon  becomes  a  serious 
pest;  but  if  every  third  year  the  land  is  put  into  some 
other  crop,  no  harm  ensues  because  the  insects  in  the 
old  cornfields  are  starved  out.  We  have  learned  that 
rotation  of  crops  is  a  good  thing,  and  "try  to  avoid  plant- 
ing two  successive  crops  of  a  similar  kind;  or  if  that 
cannot  be  avoided,  planting  or  plowing  so  as  to  avoid 
harm.  For  instance,  corn  following  old  timothy  is  bad 
practice  where  the  latter  is  liable  to  be  infested  with 
bill-bugs.  Corn  belongs  with  the  grasses,  and  the  bill- 
bugs  finding  no  timothy  when  they  emerge,  attack  the 
corn.  If  the  succession  cannot  be  avoided,  the  soil 
should  be  plowed  in  fall  and  the  corn  planted  as  late  as 
may  be.  Similar  practice  is  to  be  followed  where  root 


THE  WAR  ON  INSECTS  301 

web-worms  occur  and,  as  a  rule,  old  sod  is  better  fall- 
plowed  if  insect  injury  to  the  next  following  crop  is  to 
be  avoided.  Most  wire-worms  and  white  grubs  require 
two  entire  years  to  come  to  their  full  growth,  pupating 
or  even  changing  to  an  adult  in  the  late  fall  of  the 
second  year,  and  coming  out  as  adults  during  the 
spring  of  the  third.  Fall  plowing  at  the  end  of  the  sec- 
ond year  will  expose  these  pupae  or  recent  adults  and 
kill  them,  whereas  if  delayed  until  the  land  is  fit  the 
spring  following,  the  beetles  would  be  sufficiently  mature 
to  survive. 

The  corn-worm  and  many  similar  pests  also  pupate 
in  the  fall,  making  cells  in  which  they  lie  safely  in  all  or- 
dinary winters.  Fall-plowing  breaks  up  those  cells  and 
brings  the  soil  into  direct  contact  with  the  pupae,  which 
are  killed  by  the  contractions  and  expansions  of  the 
soil  about  them,  under  the  influence  of  frost  and  thaw. 
Of  course  fall-plowing  is  not  always  good  farm  prac- 
tice from  other  points  of  view,  and  the  grower  must 
decide  what  he  had  better  do  after  balancing  all  the 
factors  of  his  problem.  But  in  the  control  of  under- 
ground pests  this  practice  is  important.  Sometimes, 
indeed,  our  efforts  are  indirect,  as  when  in  late  fall  we 
plow  land  infested  with  root-lice  very  deeply,  to  destroy 
the  nests  of  the  ants  that  shelter  them  or  their  eggs 
during  the  winter. 

Frequently  the  time  of  planting  or  the  time  or 
manner  of  harvesting  determines  the  question  of  in- 
jury. We  have  learned  that  in  regions  subject  to  Hes- 
sian fly  attacks,  late-sown  wheat  may  be  almost  en- 
tirely free  from  infestation,  while  that  sown  early  may 
be  almost  totally  destroyed.  This  is  because  the  early 
fall  rains  bring  the  adult  flies  to  maturity  and  they  lay 
their  eggs  on  wheat  or  other  grasses  very  soon  there- 
after. Anything  that  comes  up  later  is  exempt  from 


302  INSECTS 

attack.  It  is  impossible  to  fix  an  arbitrary  date,  for 
that  varies  with  latitude,  and  even  in  the  same  latitude 
the  time  at  which  the  flies  appear  on  the  wing  is  deter- 
mined by  weather  conditions:  a  drought  may  delay 
them  until  the  very  latest  period  for  safe  sowing  has 
passed,  and  in  that  case  early  and  late  sown  are  apt  to 
be  equally  infested.  Sweet  potato  growers  in  regions 
infested  by  flea  beetles  have  learned  that  if  they  delay 
setting  out  their  plants  until  the  middle  of  June  they 
have  little  to  fear  from  the  insects;  but  if  plants  are 
set  in  May,  they  are  almost  certain  to  be  seriously 
injured.  Other  cases  might  be  cited,  but  it  is  sufficient 
to  show  that  by  a  careful  study  of  the  habits  of  a  species 
we  can  often  avoid  injury  without  a  direct  fight.  Wheat 
harvested  in  July  and  left  in  shock  is  very  likely  to 
become  infested  by  the  Angoumois  grain  moth.  Carted 
from  shock  to  mow  the  infestation  spreads  until,  in 
September  or  October  when  threshing  time  comes  round, 
a  large  percentage  of  grain  is  defective  and  "flies"  or 
"moth"  are  numerous.  If  instead  of  being  left  in  the 
fields  and  then  mowed,  the  grain  had  been  at  once 
threshed  and  binned,  there  might  have  been  a  little 
surface  infestation,  but  there  could  have  been  no  serious 
spread  in  the  bulked  grain. 

Occasionally  an  insect  can  be  diverted  from  a  more 
to  a  less  valuable  crop,  as  in  the  case  of  the  squash 
borer  which  prefers  late  squashes  like  the  hubbard  or 
marrowfats  when  it  can  get  them,  but  will  accept  sum- 
mer varieties  like  the  crook-neck  if  the  others  are  not 
present  in  equal  attractiveness.  The  grower  therefore 
plants  crook-necks  early,  and  on  the  same  ground  puts 
in  the  other  varieties  late.  The  early  vigorous  growers 
attract  the  moths,  the  plants  become  infested  but  are 
vigorous  enough  to  produce  a  crop  that  pays  for  the 
labor,  before  the  late  varieties  need  the  ground  and  the 


THE  WAR  ON  INSECTS  303 

borers  approach  full  size.  Then  the  infested  plants  are 
taken  out  and  destroyed,  borers  and  all,  leaving  the 
others  free  with  prospects  for  only  a  very  small  brood 
of  moths  for  next  season. 

That  introduces  the  matter  of  clean  culture.  It 
has  been  shown,  elsewhere,  that  some  of  our  well-known 
pests  pass  a  portion  of  their  life,  and  sometimes  an  im- 
portant one,  on  wild  plants  allied  to  the  crop  grown, 
and  these  serve  to  tide  it  over  from  one  season  to  an- 
other. Clean  cultivation  rids  the  farm  or  garden  of 
these  wild  plants  and  makes  it  more  difficult  for  them 
to  survive.  So  a  great  many  species  live  through  the 
winter  on  the  remnants  of  the  crop  they  infested,  and 
were  these  destroyed,  the  hibernating  forms  would  be 
destroyed  with  them.  It  is  a  good  general  rule,  when 
you  are  done  with  a  crop,  get  it  off  as  soon  as  possible 
and  burn  all  left-overs  that  might  shelter  injurious 
insects.  Stems  of  cotton,  cucurbs,  potatoes  and  toma- 
toes are  among  those  with  insects  so  controllable. 

If  in  all  orchards  all  dropped  fruit  could  be  kept 
picked  up  and  destroyed,  injury  from  codling  moth 
would  be  at  once  reduced  more  than  one-half;  plum 
curculios  would  soon  cease  to  be  important,  and  fruit 
flies  would  lessen  materially.  Some  work  is  done  along 
this  line  in  large  orchards,  but  as  a  rule  the  insects  in 
dropped  fruits  are  allowed  to  develop  at  will. 

Farm  animals  can  be  utilized  much  more  exten- 
sively than  they  have  been.  Sheep  and  hogs  in  an 
orchard  are  great  helps  in  disposing  of  dropped  fruits 
and  of  such  insects  as  come  to  the  surface.  A  drove 
of  hogs  in  a  sod  field  infested  with  wire-worms  and 
grubs  will  tear  it  up  and  dispose  of  a  very  large  number 
of  the  specimens  if  aided  by  a  few  shallow  furrows  to 
give  them  a  start.  Chickens,  turkeys  and  guineas  are 
great  insect  feeders  and  can  be  trained  to  follow  the 


304  INSECTS 

plow  and  pick  up  every  specimen  brought  to  view. 
Once  a  small  number  of  fowls  has  been  trained  to  this 
work,  the  flock  will  continue  the  training;  the  new 
members  following  the  older  without  additional  trouble 
to  the  farmer. 

In  the  selection  of  fertilizers  considerable  benefit 
is  sometimes  derived  in  the  use  of  minerals  rather 
than  barn-yard  manure.  Many  insects  require  the 
shelter  or  presence  of  decaying  vegetable  material, 
and  do  not  thrive  in  soils  impregnated  with  mineral 
fertilizers.  This  is  a  point,  however,  where  the  question 
of  farm  practice  is  eminently  one  for  the  cultivator,  and 
no  general  recommendations  can  be  given. 

There  are  still  among  our  battery  of  insecticides 
the  gases  and  vapors,  and  these  are  of  great  impor- 
tance. Sulphur  fumes  have  been  used  for  many  years 
against  household  insects  but  these  are  being  superseded 
by  the  hydrocyanic  acid  already  described. 

Bisulphide  of  carbon  is  a  clean,  water-white  liquid, 
very  foul  in  smell,  volatilizing  rather  slowly  at  ordinary 
temperatures,  the  vapor  heavier  than  air  and  very 
inflammable.  This  vapor  is  fatal  to  most  insects  ex- 
posed to  it  in  a  confined  space  for  an  hour  or  more, 
and  it  destroys  the  vitality  of  seed  germs  exposed  to 
it  much  over  twenty-four  hours.  It  is  rarely  used  in 
the  field,  but  for  insects  infesting  stored  products  is 
extremely  useful.  Where  entire  plants  infested  by  plant 
lice  can  be  covered  by  a  tight  cone,  jar  or  box,  one 
drachm  or,  roughly  speaking,  a  tablespoonful  to  every 
cubic  foot  of  space  will  kill  the  insects  in  one  hour. 
In  melon  or  cucumber  fields  in  which  plant  lice  have 
just  made  a  start,  it  is  sometimes  possible  to  check  their 
spread  by  treating  the  infested  hills  under  hay-caps 
or  similar  covers,  or  even  under  tubs  or  large  pails. 
Large  clam-shells  make  good  receptacles  for  the  liquid, 


THE  WAR  ON  INSECTS  305 

and  as  the  vapor  is  heavy,  the  shell  should  be  put  on 
top  of  the  mass  of  vines. 

A  much  more  usual  employment  for  the  material 
is  to  destroy  insects  infesting  seeds  like  peas,  beans, 
lentils,  wheat  or  corn.  In  such  cases  the  infested  seeds 
should  be  put  into  a  tight  box  or  other  receptacle,  and 
bisulphide  at  the  rate  of  one  drachm  per  cubic  foot 
of  space  should  be  placed  in  a  shallow  dish  on  top  of 
the  mass,  the  box  or  jar  being  tightly  covered,  of  course. 
In  twenty -four  hours  all  the  insects  will  be  killed  with- 
out injury  to  the  germinating  power,  but  if  the  seed 
is  to  be  used  for  planting,  it  must  then  be  aired  out  be- 
fore being  again  put  away.  Eggs  are  not  killed  by  this 
vapor,  hence  it  may  be  necessary  to  treat  a  second  time 
in  case  of  badly  infested  material.  If  the  grain  or  other 
seed  is  to  be  used  for  food  only,  it  may  be  kept  covered 
indefinitely,  as  no  injury  is  caused  to  its  milling  or  cook- 
ing qualities.  In  large  spaces  one  pound  may  be  counted 
for  100  cubic  feet  of  space,  or  for  one  ton  of  binned 
grain.  Shallow  vessels  should  always  be  used  for  evap- 
orating dishes  to  expose  as  large  a  surface  as  possible, 
and  the  heavy  nature  of  the  fumes  must  be  taken  into 
consideration.  Under  no  circumstances  should  the 
material  be  used  near  a  light  of  any  kind,  and  if  the 
person  using  it  has  any  regard  for  his  safety,  he  will 
not  smoke  while  handling  it  even  in  the  field. 

Before  the  development  of  the  hydrocyanic  acid 
gas,  bisulphide  of  carbon  was  used  to  treat  even  large 
spaces  like  houses,  barns  and  mills;  but  its  cost  and 
dangers  are  so  great  compared  with  the  newer  material 
that  it  is  not  now  employed  in  this  way.  Purchased 
in  small  quantities  at  drug  store  prices,  this  is  rather 
an  expensive  material;  but  there  is  a  special  much 
cheaper  grade  known  as  "Fuma"  bisulphide,  which 
answers  every  purpose  for  agricultural  use. 

20 


3o6  INSECTS 

Hydrocyanic  acid  gas  is  produced  by  the  action  of 
dilute  sulphuric  acid  on  cyanide  of  potassium,  and  is 
intensely  poisonous  to  all  animal  life.  It  effects  vege- 
table life  to  a  somewhat  less  extent  and  more  slowly, 
so  that  there  is  usually  a  fair  margin  of  safety  between 
its  effectiveness  on  insects  and  the  danger  of  injury  on 
plants.  For  the  destruction  of  insects  on  dormant 
nursery  stock,  and  for  the  treatment  of  rooms  and 
buildings  to  destroy  household  or  other  pests,  the  fol- 
lowing formula  answers  for  100  cubic  feet  of  space: 

Cyanide  of  potassium,  90%  pure  (by  weight) . . .   i  ounce 

Sulphuric  acid,  sp.  gr.  1.83  (by  measure) 2  ounces 

Water 4  ounces 

The  gas  is  lighter  than  air  and  is  generated  in  an 
earthenware  jar,  pot  or  basin  as  follows:  First  pour  in 
the  water,  add  the  acid  slowly,  and  finally  drop  in  the 
cyanide  broken  into  small  lumps  in  a  thin  paper  bag. 
The  order  of  mixing  is  important,  for  if  the  water  be 
poured  into  the  acid,  the  amount  of  heat  suddenly 
developed  will  be  so  great  as  to  spatter  the  material 
in  every  direction.  The  cyanide  is  dropped  in,  bag 
and  all,  to  somewhat  delay  the  development  of  gas  and 
permit  the  operator  to  escape  or  close  the  fumigating 
chamber.  The  method  of  dealing  with  household  pests 
has  already  been  given.  Greenhouse  fumigation  forms 
a  study  by  itself,  because  of  the  difference  in  effect  on 
the  many  sensitive  plants  there  raised,  and  for  which 
no  generally  applicable  directions  can  be  given. 

Orchard  fumigation  is  not  much  practised  in  the 
east  where  most  of  the  trees  have  a  dormant  season 
permitting  their  treatment  with  sprays.  On  the  Pacific 
coast,  fumigation  of  citrus  and  olive  trees  is  quite  largely 
practised  and  elaborate  apparatus  for  covering  trees 
with  gas-tight  tents  is  in  use.  But  even  there  the  prac- 


THE  WAR  ON  INSECTS  307 

tice  is  not  yet  finally  settled,  and  an  extensive  series 
of  experiments  is  in  progress  to  determine  the  most 
effective  methods.  Under  these  circumstances  no 
more  is  needed  here  than  a  reference  to  the  matter, 
emphasizing  its  extent  and  importance. 

By  no  means  all  the  materials  used  in  the  fight  against 
insects  have  been  enumerated  here;  a  few,  like  gasoline 
and  Delphinium  are  of  very  limited  application  and 
have  been  referred  to  in  other  connections.  But  enough 
has  been  said  to  show  the  chief  weapons  in  our  battle 
with  the  tiny  foes  that  influence  us  so  much  more  than 
is  generally  known.  What  is  not  told  is  the  number 
of  materials  and  combinations  that  have  been  tried 
and  rejected,  before  those  here  enumerated  were  fully 
tested  out  and  approved.  In  the  reports  and  bulletins 
of  agricultural  departments  and  experiment  stations, 
almost  every  year  brings  records  of  trials  made  of  new 
combinations;  some  originated  by  the  experimenters, 
some  produced  by  inventors  or  manufacturers  who 
believed  they  had  discovered  something  better  than 
was  ever  known  before.  Out  of  all  these  experiments 
very  little  is  annually  added  to  our  battery;  but 
the  limitations  of  the  older  materials  are  becoming 
ever  better  understood  and  the  number  of  effective 
combinations  is  larger  now  than  ever  before. 

And  so  in  the  machinery  for  applying  insecticides 
and  fungicides  there  is  an  enormous  and  continuing 
progress.  A  collection  of  dusters  and  sprayers  dating 
only  ten  years  back  now  seems  antiquated  and  ineffec- 
tive, and  as  our  methods  of  application  become  perfected, 
the  benefits  derivable  increase. 

From  the  practical  standpoint  man  now  carries  on 
his  war  against  insects  absolutely  without  regard  to 
the  natural  checks  of  that  insect,  if  it  be  a  native.  If 
it  be  an  introduced  species  his  attempt  is  to  restore  the 


3o8  INSECTS 

natural  balance  by  introducing  the  natural  checks  as 
well,  and  beyond  that  he  relies  on  his  own  efforts. 

We  have  learned  to  take  advantage  of  the  weak 
points  in  the  life  cycle  of  a  troublesome  species,  and 
we  know  that  there  is  at  least  as  much  in  the  proper 
application  of  insecticides  as  in  the  insecticides  them- 
selves. As  there  is  a  continuous  specialization  in  the 
raising  of  crops,  so  each  grower  learns  to  deal  with  the 
pests  of  that  crop  by  experiment  and  observation. 

It  is  beginning  to  be  realized  that  numbers  of  speci- 
mens are  not  a  measure  of  the  difficulty  in  dealing 
with  pests.  Mosquitoes  are  abundant  enough  in  exam- 
ples, but  their  life  cycle  is  simple  and  the  methods  of 
control  are  obvious.  The  old  cry  "it  can't  be  done" 
has  not  even  yet  ceased,  in  the  face  of  the  results  ob- 
tained in  Cuba,  Panama,  and  New  Jersey.  And  yet, 
after  all,  it  is  simply  a  matter  of  dealing  with  many 
breeding  places  in  the  same  way,  and  when  a  problem 
is  reduced  to  a  mere  matter  of  amount,  it  is  a  matter 
of  time  and  dollars  only  to  get  it  done. 

Flies  are  even  more  universally  distributed  than 
mosquitoes,  and  from  the  sanitary  standpoint  yet 
more  dangerous;  but  even  they  will  not  escape  man's 
efforts  at  control.  The  campaign  has  been  already 
begun  and  no  doubt  it  will  be  continued  until  practical 
measures  for  checking  fly  development  are  universal. 

To  one  in  the  forefront  of  the  battle  progress  some- 
times seems  distressingly  slow,  and  results  small  out 
of  all  proportion  to  the  efforts  made;  but,  after  all, 
a  review  extending  back  a  decade  or  two  shows  that 
neither  the  entomologist  nor  those  for  whom  he  has 
labored  need  be  ashamed  of  the  advances  made.  At 
all  events  the  importance  of  insects  in  their  relation  to 
man  has  come  to  be  fully  realized. 


INDEX 


Adhesives,  295 

Air-slacked  lime,  294 

Angoumois   grain   moth,    242, 
302 

Animal  feeders  on  insects,  131 

Anopheles  and  malaria,  204 
habits,  211 

Ant  guests,  128 
lions,  89 

Ants  and  plant  lice,  125 
and  Scutellista,  127 
as  scavengers,  190 
domestic  economy,  125 
in  houses,  242 

Aphelinus  on  scales,  119 

Aphis  lions,  89 

Apple  borers,  65 

Argentine  ant,  245 

Arsenate  of  lead,  274 

Arsenical  poisons,  274 

Asiatic  lady-bird,  107 

Asilidae,  no 

Balance  of  nature,  249 
Banding,  uses  of,  298 
Bark-beetle  injury,  70,  268 
Barriers  to  canker  worms,  298 
Bat-tick,  183 
Bean  weevils,  66,  261 
Beaver  parasite,  161 
Bed-bugs,  229 
Bee  disease,  151 

flies,  no 

habits,  26 

products,  195 
Bees  as  pollenizers,  25 


Beetles  as  borers,  267 

as  parasites,  96 

as  pollenizers,  36 

injury  by,  58 
Bill  bugs,  259 
Bird  lice,  160 
Birds  vs.  insects,  133 
Bisulphide  of  carbon,  304 
Biting  lice,  159 
Black  beetles,  227 

flies,  167 

Blastophaga  on  figs,  31 
Blister  beetles,  97,  197 
Blood  of  insects,  10 
Blow-fly,  175 
Blue-bottle  fly,  174 
Body  louse,  156 
Boll-worm,  263 
Bombyliidae,  no 
Book  lice,  221 
Bordeaux  mixture,  275 
Borers  as  food,  197 

protections  from,  297 
Boring  caterpillars,  266 
Bot-flies,  176 
Bran  and  arsenic,  297 
Breathing  of  insects,  10 
Breeding  of  insects,  1 5 
Bristle-tails,  219 
Bruchidae,  66,  261 
Buffalo  gnats,  166 

moth,  233,  234 
Bumble-bees  and  clover,  25 
Buprestidae,  60 
Burying  beetles,  188 
Butterflies  as  pollenizers,  34 


3°9 


3io 


INDEX 


Cabbage  maggot,  82 
Caddice-flies,  91 
Cantharides,  197 
Carbolic  acid,  291 
Carbon  bisulphide,  304 
Carpenter  worms,  74 
Carpet  beetles,  233 
Carrion  beetles,  188 
Caterpillar  diseases,  149 
Cattle  bots,  180 
Caustic  potash,  292 

soda,  292 

Cecidomyiid  injury,  81 
Centipedes  in  house,  218 
Cerambycidae,  64 
Chicken  flea,  165 

lice,  1 60 
Chilocorus  bivulnerus,  106 

similis,  106 
Chinch-bug  disease,  145 

injury,  53 
Chitin,  1 6 

Cholera  and  flies,  199 
Chrysanthemum  fly,  37 
Chrysomelidae,  64 
Chrysopidae,  89 
Cicada  disease,  148 

injury  by,  52 
Cigarette  beetle,  237 
Circulatory  system,  10 
Clavicorn  beetles,  187 
Clean  culture,  251,  303 
Clerids  vs.  Scolytids,  108 
Click  beetles,  59 
Climate  and  insects,  138,  144 
Clover  pollination,  25 
Clothes  moths,  238 
Coccinellidae  habits,  102 
Cochineal,  196 
Cockroaches,  227 
Codling  moth,  262 
Coleoptera,  18 


Coleoptera,  as  parasites,  96 
as  pollenizers,  36 
injury  by,  58 
Coleopterous  borers,  267 
Complete  metamorphosis,  17 
Contact  poisons,  276 
Corn  bill-bugs,  259 

worm,  263 

Cossids,  injury  by,  73 
Cotton-boll  weevil,  141,  261 
Cottony  cushion  scale,  105 
Crab  louse,  158 
Crane-flies,  80 
Crickets  in  house,  225 
Crop  remnants,  303 
Croton  bugs,  227 
Crude  petroleum,  285 
Culex  and  disease,  207 
Culicide,  213 
Currant  worm,  77 
Cutting  out  borers,  300 
Cut -worm  injury,  259 
Cynipid  injury,  78 

Deer  flies,  169 
Dermestidae,  189 
Dermestids  in  house,  232 
Destroy  crop  remnants,  303 
Digger  wasps,  1 1 6 
Diptera,  20,  190 

as  pollenizers,  37 

injury  by,  80 

predatory,  109 
Diseases  and  insects,  199 

of  insects,  138,  144 
Dragon  flies,  92 
Drug  beetle,  237 
Dry  hydrate  of  lime,  294 

powders,  276 

Ears  of  insects,  13 
Earwigs,  habits  of,  53 


INDEX 


Egg  stage,  15 
Elateridae,  59 
Ephemeridae,  87 
Eyes  of  insects,  13 

Factors  favoring  insect  injury, 

251 

Fall  plowing,  301 
Fallen  fruits,  303 
Farm  animals,  use  of,  303 
practice,  300 

and  insect  injury,  259 
Fecundity  of  insects,  84 
Feeling,  sense  of,  13 
Fertilizers   for   insect    control, 

3°4 

Fifteen-spotted  lady-bird,   104 
Figs,  pollination  of,  30 
Filariasis  and  mosquitoes,  207 
Fish-moths,  219 
Flat-head  borers,  60 
Fleas,  162 

as  disease  carriers,  213 

development  of,  215 
Flies  and  sleeping  sickness,  208 

as  disease  carriers,  199 

as  pollenizers,  37 

as  scavengers,  190 

blood-sucking,  166 
Flour  beetles,  236 
Fly  disease,  144 
Foul  brood  in  bees,  151 
Fowls  vs.  insects,  137 
Fruit  flies,  83 
Fumigating  dwellings,  246 
Fumigation,  306 

for  mosquitoes,  213 
Furrows  as  barriers,  300 

Gall  midges,  80 

wasps,  77 
Galls,  uses  for,  197 


Gas-tar  protectors,  298 
Geographical  distribution,  139 
Golden-eyed  flies,  170 
Grape  phylloxera,  252 
Grasshopper  disease,  144,  147 

injury,  54 

Grasshoppers  as  food,  196 
Green-heads,  169 
Ground  beetles,  101 

Hand  picking,  299 
Head  louse,  156 
Hearing  of  insects,  13 
Heart  of  insects,  10 
Hellgrammite,  88 
Hellebore  as  insecticide,  296 
Hemiptera,  18 

as  animal  parasites,  1 53 

feeding  habits,  41 

habits  of,  93 
Hepialid  injury,  74 
Hessian  fly,  81 
Heteromera,  food  habits,  67 
Histeridae,  189 
Honey  bees,  195 

dew,  256 

Hopper  dozers,  299 
Horn-fly,  171,  254 

-tails,  injury  by,  77 
Horse  bot,  178 

flies,  no,  169 

manure  and  arsenic,  297 
House  ants,  242 

fly,  200 

mosquito,  208 
Household  insects,  217 
Hydrocyanic  acid  gas,  246,  306 
Hymenoptera,  20 

injury  by,  75 

predatory    and    parasitic, 

H5 
Hyper-parasitism,  124 


3I2 


INDEX 


Incomplete  metamorphosis,  1 7 
Indian-meal  moth,  242 
Injury  caused  by  insects,  269 
Insect  powder,  276,  277 
Insecticide  machinery,  299 
Insects  as  disease  carriers,  199 

as  food,  196 

as  medicine,  197 

denned,  10 
Instars  =  stages,  15 
Introduced  insect  pests,  252 

plants,  252 

Jigger  flea,  1 63 
June  bugs,  63 

Katydids,  57 
Kerosene,  286 

emulsion,  287 

Lace-wing  flies,  89 
Lace-insects,  195 
Lady-bird  beetles,  102 
Lamellicornia,  62 
Lampyridas,  108 
Larder  beetles,  1 89 
Larval  stage,  15 
Leaf -feeding  insects,  258 

hoppers,  injury  by,  257 
Lepidoptera,  20 

as  parasites,  161 

as  pollenizers,  34 

injury  by,  72 

predatory,  109 

Machinery,  299 
Malaria,  how  carried,  203 
Mantids,  habits  of,  95 
Mantispidae,  90 
May  beetles,  63 
flies,  87 


Meadow  grasshoppers,  56 
Meal  snout-moth,  242 

worms,  235 
Mecoptera,  90 
Meloidae,  habits  of,  97 
Metamorphoses,  15 
Midges,  167 

injuries  by,  261 
Migration  of  insects,  140 
Mineral  oils,  285 
Miscible  oils,  288 
Moisture,  effect  of,  142 
Moulting  of  insects,  1 5 
Mosquitoes  and  malaria,  204 

and  yellow  fever,  206 
Moths  as  pollenizers,  34 
Muscles  of  insects,  12 
Museum  beetles,  234 
Myrmeleonidas,  89 

Neuroptera,  18,  88 

feeding  habits,  41 
Nervous  system,  12 
Nut  weevils,  67,  262 
Nymph,  17 

Odonata,  habits,  92 
(Estridas,  176 
Onion  maggot,  82 
Oriental  roach,  227 
Orthoptera,  18 

injury  by,  53 

Ox-bot,  1 80 

Pain,  sense  of,  14 
Paper  disks  for  root  maggots, 
298 

protectors  for  trees,  298 
Parasitic  flies,  113 

hymenoptera,  120 
Parasitism  on  vertebrates,  153 
Paris  green,  274 


INDEX 


Pea  weevils,  66,  261 
Peach-tree  borer,  72 
Pear  midge,  81,  254,  262 
Perception,  sense  of,  14 
Periodical  cicada,  52 
Phasmids,  injury  by,  53 
Phylloxera,  252 
life  cycle,  46 
on  grape,  46 
Pill  beetles,  189 
Pirate  bugs,  94 
Plague  and  fleas,  214 
Plant-beetle  injury,  63 
lice  and  ants,  125 

and  weather,  143 
development,  43 
disease,  148 
injury  by,  42,  255 
parasites  on,  119 
remedies,  277 
sexual  parts,  21 
Planting,  time  of,  301 
Plasmodium,  203 
Platypsylla,  161 
Platyptera,  87 
Plecoptera,  87 
Plum  curculio,  262 
Pollination  by  insects,  22 

by  wind,  22 
Polyembryony,  122 
Pommace  flies,  191 
Potato  beetle,  249 
Potter  wasps,  1 1 6 
Powder-post  beetles,  238 
Predatory  beetles,  100 

insects,  86 

Pronuba  and  yucca,  24 
Protective  resemblance,  131 
Psorophora,  109 
Psocids  in  house,  221 
Ptinids  in  houses,  237 
Pupal  stage,  16 


Pupipara,  182 
Pyrethrum,  277 

Raphidiidae,  90 
Reason  in  insects,  14 
Reduviids,  habits  of,  94 
Reproduction,  organs  of,  15 
Resin  soap,  296 

washes,  290 
Rhynchophora,  67 
Roaches,  habits  of,  95,  226 
Robber  flies,  no 
Root  lice,  46 

maggots,  82 
Rose-chafer  injury,  258 
Rotation  of  crops,  300 
Round-head  borers,  64 
Rove-beetles     as     scavengers, 

187 
habits  of,  102 

San  Jose"  scale,  51 
Saw-fly  injury,  76 
Scale-insect  disease,  147 

injuries,  49,  256 
Scale  insects,  development,  49 
Scales,  parasites  on,  119 

remedies  for,  280 
Scavengers,  insects  as,  185 
Scolytid,  injury,  70 
Scorpion  flies,  91 
Screw-worm  fly,  173 
Senses  of  insects,  13 
Sesiids,  injury  by,  72 
Sheep-bot,  177 

ticks,  182 

Sight  of  insects,  13 
Signate  lady-bird,  105 
Silk-worm  disease,  151 
Silk-worms,  192 
Silver-fish,  219 
Simuliidae,  166 


INDEX 


Sinuate  pear  borer,  254 
Skin  of  insects,  16 
Smell,  sense  of,  13 
Smilia  misella,  106 
Snout -beetle  injury,  67 
Soaps  as  insecticides,  278 
Soldier  beetles,  108 
Soluble  oils,  288 
Squash  borer,  72,  302 
Structure  of  insects,  9 
Stable  flies,  171 
Staphylinidae,  187 

habits  of,  102 

Stegomyia  and    yellow    fever, 
206 

habits,  210 
Stem  borers,  265 
Stone  flies,  87 
Stylops,  habits  of,  96 
Sulphur  as  an  insecticide,  285 

soap,  285 
Syrphids  vs.  plant  lice,  1 1 1 

Tabanidae,  no,  169 
Tachinid  flies^as  parasites,  113 
Tactile  structures,  14 
Taste,  sense  of,  13 
Temperature,  effect  of,  140 
Termites  in  house,  222 
Thalessa,  habits  of,  121 
Thripids  and  dry  weather,  142 
Thysanura,  17 

feeding  habits,  40 
Thysanurids  in  house,  219 
Time  of  planting,  301 
Tobacco,  277 
Tracheae,  10 


Transformations,  15 

Trap  crops,  302 

Tree -hoppers,  injury  by,  52 

protectors,  298 
Trichoptera,  habits,  91 
Tsetse  flies,  207 
Tumble-bugs,  189 
Typhoid  fever  and  flies,  200 

Vedalia  cardinal! s,  105,  253 
Vertebrate  enemies  of  insects, 
130 

Walking  sticks,  53 
War  on  insects,  271 
Warbles,  180 
Warning  colors,  132 
Wasps,  predatory,  115 

social,  118 

solitary*  115 
Weather  vs.  insects,  138 
Whale-oil  soap,  279 
Wheel-bug,  94 
White  ants  in  house,  222 

fly  in  California,  141 

grubs,  63 
Winter,    effect    of   on    insects, 

M3 

Wire -worms,  59 
Wood-boring  beetles,  60 

-leopard  moth,  73 
Woolly  apple  louse,  257 

Yellow  fever  and  mosquitoes, 

206 
Yucca  pollination,  23 


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